When you speak of a 12,000 grit stone be sure and obtain the Chinese 12000 grit waterstone from www.woodcraft.com. That hone I use for every razor that I sharpen. It does make a difference but it is very slow cutting. I usually need 50-100 laps on that hone. The degree of change is noticeable.
You might also want to consider the classic Belgian coticule waterstone as an alternative to the 12,000 stone.

I have no experience with the Kitayama or Shapton stones so I will not comment on those.

Hope this helps,