I have been reading about japanese knife options and have seen all of these stone combinations that people come up with.  It's unnecessary and expensive to have so many stones.  I have a woodworking background, and need to quickly sharpen blades all the time.   You need two stones.  One is the "honing" stone.  This is 800 - 1200.     The second is the "polishing" stone.  This is 4000 - 8000.  8000 is a near mirror polish.  Anything higher is overboard.  And costs...