First beginner's prep knife & What bevel angle

Lots of questions here, I'll do my best to answer them.

Get a 10 inch knife, or a 240mm gyuto. If you have space, and the will to learn maybe a 270mm gyuto. I have a 210mm, and although I love the knife, it rarely gets used as its just too short.

Properly sharpened, a Forschner will hold up to it. But, it will need steeling - alot. I'll presume you know how to steel a knife, if not, BDL has a great guide on his site as to how to do it. There is also one good video that I've seen on youtube (http://www.youtube.com/watch?v=jAWcQOc93ec)

I'd probably say the next step up from the Forschner is the Artifex, but I won't talk about it because I've never been in contact with one. FWIW, I think that the Artifex is as good as the CN, and a lower price. But, you don't have the range in sizes, and if you're outside the US, then the CN will probably work out cheaper because JCK are amazing at postage and keeping taxes down. I paid 7$ and no tax for my CN, vs the +40$ and unknown tax I'd have paid on an Artifex. That said, a knife is a BIG investment. Don't skimp on it. Get what you really want, because you'll end up buying it anyway.

I haven't seen many used Japanese knives for sale on ebay, although there is a forum for it here. Irregardless, if you aren't very confident in being able to sharpen, set a bevel and fix any problems the previous owner has caused, I'd steer away from used knives. 

You need to tell us:
Stainless or carbon?

Budget?

Location?

How good are you at sharpening (honestly)(no really, be honest with yourself if not us)

How much are you willing to invest in sharpening? Both time learning and cash for stones?

Your second question;

The bevel is dependent on the knife. You'll probably get told 15-18 degrees. Single bevels aren't really worth talking about here IMO, because you're looking for an all purpose knife, and a double will just be easier.

All angles should hold the edge for the same time, given the same usage. A more acute bevel will be more prone to chipping if you do crazy stuff with it, such as chopping bones or dropping it, but will give more percieved sharpness. A more obtuse angle will take more heavy abuse, but will feel duller. You personally have to find an angle that balances the damage caused to the blade with how much care etc you're willing to give the knife.

Plastic boards are fine, as long as they are the right kind of plastic. I'd presume in a commercial kitchen that they are okay. I tend to be able to 'feel' when a board is doing bad to the edge.

By double bevel, I meant a V (conventional) rather than a \| (something you'd find on a Deba or Yanagiba). I think I may have mis-understood you there.

The most common hone I've seen recommended is the Idahone fine ceramic from CKtG. 'GR style' probably won't damage the hone, but it may damage your knife. That said, banging against a ceramic hone may snap it.

With a 50USD budget, you'll struggle to find something better than a Forschner IMHO. BDL or someone else will have to come in on the CN v Artifex issue, I don't feel I should comment on it as I'm not informed enough. What I can say, is that the CN is slightly heavier, and has a slightly wider blade. Almost the same thickness, and from what I know, the Artifex comes from the factory MUCH sharper than the CN.

Personally, given your situation I'd probably go for a 240mm Artifex.

One last question though, while at work, are your knives 'safe'? Will people use them, carelessly or without asking, and if so how much will you protect them? Is it likely for someone to (try) steal it?

As far as knives go, there is no "right kind of plastic,"  and plastic boards are not "fine."  They're very hard on knives, especially sharp ones, and tend to create chipping.  What happens is that when a knife is brought down on the board it will cut into it.  If the user torques the blade even slightly, a plastic board will grip the knife and stress the edge.  The flexible fibers in wood boards, especially end-grain wood boards, open wider, don't hold the knife as hard, flex if and when the knife is torqued, release the knife more easily, then close and "self-heal."  Unfortunately, you don't control what they have at work. 

Victorinox Fibrox and Rosewood series knives are made with a very tough, relatively soft steel which doesn't break easily.  So, they're one good choice to use on plastic boards.  However, they get dinged out of true fairly easily and require plenty of steeling on a rod hone.  Your edges will easily last a shift or two, but you'll have to steel them at least every hour.  Steeling, by the way, is something that nearly everyone does wrong.  When it comes to knives and knife maintenance, Alton Brown is an ass and Gordon Ramsay a donkey.  Read Steeling Away.

The Idahone "fine" ceramic (which CKtG calls "1200") is a fantastically good rod for very little money.  I recommend it highly. 

If you're worried about dropping a ceramic rod and breaking it, get the DMT CS2 which is reinforced with an internal metal core.  For whatever reason CS2s ship with a lot of ceramic crud (aka "refractory blow-back") on the rod, and you'll want to sand it off before using it.  The CS2 is a good rod when you get it cleaned up. 

On to knives:

The Artifex is a very nice and huge bang for the buck.  So is the CarboNext.  So are the Fujiwara FKM and Tojiro DP.  The FKM stands out from the group, but not in the good way, because its made from a very mundane alloy.  Each of the others uses something more expensive and exotic, will take a better edge than the Fujiwara, and will hold it for a longer time. 

The Richmond Artifex was designed to put the best available, high-priced, stainless alloy at its best possible hardness, in a comfortable, and inexpensive package.  In fact, it was designed for someone exactly like you doing exactly what you do.  In terms of what you're looking for, it's probably the ideal knife in every way but price.  The only thing the Artifex lacks is a bolster to improve its cosmetics.  The Artifex is made from AEB-L which can be made very sharp fairly easily.  It will get sharper than a Forschner, and need less frequent steeling; although any knife that goes through the abuse your job entails is going to need to be trued on a regular basis.

What makes the Kagayaki CarboNext special is its semi-stainless alloy.  It's a good handling knife which takes and holds a great edge for a long time.  The comparison is to the Kikuichi TKC, another semi-stainless gyuto, and not to the Masamoto VG.  The TKC and VG are just under $200 and so far out of your price range, they're not worth discussing.  There are some minor issues with CN quality control and F&F, but they're minor -- with one exception.  The blades often ship with a very poor edge, and JCK's extra-cost sharpening service doesn't help.  That means that if you're going to buy a CN you need to be prepared to profile and sharpen your own edge, or have someone to do it for you.  Because you don't sharpen well, and because most restaurant knife services don't know how to handle high end Japanese knives, at this stage of the game the CN doesn't seem like a realistic choice for you. 

The Fujiwara FKM is a nicer looking, more upscale, and better handling knife than the Forschner.  Otherwise it possesses most of the same virtues and vices.  The handle is a bit on the skinny, short side.  If you have very large hands and/or like to hold the knife at or behind the bolster, you might find that a problem.  Assuming the handle's okay, is its better handling, French profile make it worth twice as much as a Forschner?  Yes.  Does its cosmetics make it the equal of an Artifex?  No.

Compared to the other three Japanese knives the Tojiro DP is stiffer.  It takes a better edge than the FKM, but not quite as good as either of the other two.  The handle is somewhat large and boxy.  Considering what you put a knife through, you might find the DP chip prone. 

All of the knives we're talking about can and should be sharpened to 15*.  The Forschner comes from the factory with a 20* edge angle, but does a good job of holding 15* without collapsing. 

The Forschners can be sharpened equally well on oil stones and water stones.  You'll find oil stones too slow for the others, they want reasonably good quality water stones.   

The Artifex and Forschner probably come closest to answering your questions.  I think the Artifex is well worth the extra $50, but $50 means a lot more to you than it does to me. 

BDL

The Norton IB-8 is a combination India oil-stone.  Like other oil stones it's not made with a "binder," at least not in the same way water stones are.  My reference to Norton's clay binders was to their water stones.  They're decent stones, but have been obsolete for years.   They're overpriced for what they are. 

A Norton IB-8 has two surfaces.  One is a coarse India, the other a fine India.  "India" is Norton's trade name for their Aluminum Oxide/ceramic synthetic stones.  Like most oil stones, India stones work best with tough, soft alloys like the one Forschner uses.  The coarse India is too coarse for anything but profile and repair.  The fine India is a good surface for starting an edge, but is still very coarse for a finishing edge.  If you're going to use Indias as part of your sharpening kit, you want to follow them with something finer like a hard, black or translucent Arkansas. 

I occasionally sharpen some of my old European made knives with an oil stone kit which has an IB-8, a Hall's Soft Arkansas, and a Hall's Surgical Black Arkansas.  From a "grit screen" standpoint the fine India and soft Ark are so close that the soft Ark shouldn't be necessary; but it does something to the edge which allows the black to work much better, and is worth the little bit of extra time.  However, you could get away without the soft Ark, use a hard Ark for finishing (much less expensive than a black) and save yourself a few bucks.  If you're going to buy Arkansas stones buy from a good quarry.  I suggest limiting yourself to  Hall's Proedge, Dan's or Norton. 

If you're going to buy an Artifex, I think you'd serve yourself much better with water stones.  Considering how you're fighting with your budget you might want to start with a King 800/6000 combi stone. 

BDL