57, I've heard good things about going up to 3000 with a DA. I'm still stopping at 2000 by hand, but it still is coming out pretty nice. This is on Forester green single stage, which is still pretty dark and shows scratches pretty easily.
Michael, I usually run in the 1500-2000RPM range with my Makita. About number 3 or a little above on the speed control dial.

Bob