you can set the board to let you up by 1 Mhz increment. Try using values between 166 and 200. You have 34 Mhz there (a lot) that you can play with.
I did have the same with my CPU. I never unlocked it, but it overclocked fine (Thoroughbred 2500+) and there were a couple of multipliers that were together. I believe the list is pretty much as you posted. I can check it up tonight when I go home