Tunze and Ecotech Vortechs are highly regarded. They can be controlled to provide turbulent flow which is really, really nice if you want to have SPS corals. LPS corals and soft corals are less demanding.
I saw that BRS, bulk reef supply, had you tube videos showing the flow patterns produced by various power heads. If you go to the BRS or Marine Depot web site you can see how well people review various power heads.