Terrance said:how much money would you like to spend on flow?
Since you posted in the reef section, I'm assuming you want a reef. Flow is important for a successful reef since different corals like different flow (rockscaping will factor into flow).
I would suggest going with the Hydor Koralia Evolution line of powerheads. They are by far the most popular lower price powerhead out there right now. they have great reviews, flow, and durability. As for which one, I am not sure how much flow you are looking for but I would go with 2 or 3 smaller ones rather than 1 large one so you can have a little more dynamic flow in your tank.
2 koralia 750s plus your return should be a good start.