No. I'm not saying you want to get a double-sided stone. I'm not saying you want to get anything. I was translating what Franz said because you'd misunderstood. I neither agree nor disagree with the recommendation to get a combination (i.e., double-sided) stone. Combi stones are initially less expensive than two single stones, but they have disadvantages.
I also neither agree nor disagree with the suggestion of a 6000# (JIS) finish for your Shun. I can think of several 6K stones which would be excellent final stones, but can also think of just as many 5Ks and 8Ks.
Throwing around grit numbers like "600" is meaningless without other context. There are not only several popular but unrelated standards, grit numbers don't translate well from stone to stone, even if the numbers come from the same system. I don't care what another student at your school uses, other than to hope he's happy. When I wrote that a King 800 was too coarse as the final stone for a Mercer, general-purpose chef's knife, I was offering you the benefit of my experience. You're free not to take my advice.
If you're cutting through chicken bones with your Shun, the Shun won't last long.
Get the Mercer sharp, and use that for all your heavy duty tasks, like breaking chickens, portioning ribs, cutting through thick-skinned squash, breaking pineapples, etc. It's better than the Shun for those because it's more durable and the edge wears very slowly and can usually be easily restored on a steel. Shun maintenance can be a little more demanding but the Shun is so much better for everything else that the extra trouble is well worth it.
And by the way, that's not an endorsement of Shun. Just for the record, Shun chef's knives are not a great choice for for most people. Yes, they're better than Mercer, but "etter than Mercer" isn't saying much.
If you want me to recommend a high quality but affordable water stone kit which will serve both your Shun and your Mercer, as well as any other knives you're likely to buy in the future: Bester 500, Beston 1200, and Suehiro Rika (3K - 5K), depending on how you use it); but hold off on using the Bester until you can consistently sharpen with both of the other stones. In addition to the stones themselves, you'll also need some sort of method for flattening them before you use them for the first time. Water stones are not packed "ready to go."
As a matter of purely personal preference, I like oil stones over water stones for my knives which are made from tough alloys (such as your Mercer); and water stones over oil stones for my knives which are made from strong, hard alloys (like your Shun). However, if you're on a budget I don't think the practical differences between oil and water stones is worth the expense and effort of two different sets.
Edited by boar_d_laze - 3/23/13 at 10:57am