I'm not familiar with the Wusthof stones you have but if you're happy with them there is no need to replace them.
If you want to refine the edge more the Shapton Glass 8K would work perfectly well as a finishing stone for your kitchen knives. I don't usually recommend the 16K for kitchen knife sharpeners. If you're sharpening straight razors then it will do well on those. Try a strop instead. It's much less money and easy to use and you can use it for quick touch ups between sharpenings in place of a rod. This strop set is less than half as much as the Shapton 16K: http://www.chefknivestogo.com/haamstkit.html