I've never used powerheads, but I have had flow over 10x the tank volume at times in the past. I've never seen too much flow on a Malawian or Victorian tank.
Right now my most impressive would be 2 Emperor 400s (400 gph each) on a 100 gallon.
My other tanks have sponge filters mainly - no idea what the GPH flow is, but I'm sure it's low (and it's best that way!).