another suggestion if you can find it...
http://www.aquariacentral.com/forums/showthread.php?t=139094&highlight=powerhead
I have gotten 2 of these, and they're really compact, plenty of flow, and have a prefilter to boot. adjustable flow rate, low voltage power supply, venturi... I love them. I packed the first one with filter media and burned it out over 6 months, and the second one i haven't mistreated, runs great, but I'm not currently using it in anything. The only drawback is that it doesn't seem like you can remove the impeller.
I could not find these for sale online, got mine in chinatown for around 25 bucks. I can see if they have more next time I'm in there or you can call Win aquarium on Mott St. NYC, he was importing them for a while and just selling off the stock.