Foodie518 is right about sharpening as a priority. What you will find is that with Japanese knives, you will not always be going through a progression of stone grits every time you sharpen. Rather, when you initially sharpen, you will go through the progression of grits. Then, you will be using your highest grit stone for maintaining the sharpness on a very frequent basis (every few days, or even daily), and the other stones occasionally for when the knives need more work than the fine grit stone can provide (such as thinning behind the edge).
You currently have Sabatier knives. Can you tell us the brand? And, if you know, can you tell us the model lines? Are the blades carbon or stainless steel?
I ask, because there's a bit of difference between brands and quite a bit of difference between carbon Sabatiers and stainless ("Inox") Sabatiers.
Foodie518 suggested a MAC Pro chef's knife. MAC Knives are all stainless.
But if you are willing to look at a MAC, please be advised that MAC Knives are only sold through authorized national distributors, and the listed authorized distributor for France is MAC International. The web site listing distributors by country is: http://www.mac-international.com/contact.htm
Since you are in the European Union, you might try one of the other European Union site distributors.
If the Mac Pro (MBK-95) is more expensive (€ 198,00) than you are comfortable with on spending for a single knife, then you might consider the Mac Chef Series BK-100 chef's knife, at € 119,00.. Same steel as the MAC Pro, same thickness, and I personally cannot find any difference in stiffness between the two knives. The principal difference is the lack of a metal bolster and a slight angle difference in the angle between the handle and the principal flat of the blade.
For a Japanese carbon blade, I'm going to refer you to a list drawn up by a former participant on this forum, Boar D. Laze, who listed a number of excellent Japanese knives on one of his blogs, here: http://www.cookfoodgood.com/?p=190
Mind you, the list is somewhat dated (6 years old). And BDL is / was very personally opinionated. And the list really isn't linked to any purchasing sites, so you will need to decipher a bit of the names and references.
But, it's a list which gives you reasons for why BDL liked or was willing to give the benefit of the doubt to a significant number of knives.
And it's a start.