First thing you need to understand is that nearly ALL electric fan manufacturers exaggerate their CFM statements by some degree. That being said as Itoldyouso has stated SPAL makes a excellent unit which will meet your needs. Another excellent product is made by Cooling Components Inc (who happen to be owned by Walker Radiator).

If you really want exceptional cooling, don't forget to add a shroud. Buy one or make your own, what matters is that you use one.