good circulation using powerheads helps filter, and maintain good gas exchange in the tank, its recommended in all tanks except tanks with seahorses and the such.
Usually 10x the gallons of your tank, so 550 GPH should be adequate. I just got 3 maxi jet 900s (230 GPH) off ---- for around $50.
The maxi jet powerheads seem to be well liked, and I have not had any problems.