200x10 would probably be better with 6/6 FSB/RAM so they clocks are in sync, should improve performance very slightly.
Plus the clock speed will still be ~2GHz, so no difference there.
There *shouldn't* be any real downside if your motherboard can handle 200MHz, and you will see a small increase in performance, but not an awesome amount (I wouldn't expect).
You might as well try it anyway, see what happens, if you only run it for a bit it won't kill your system.