Steve-O hit it on the mark. A few low rpm 120mm or a 200mm pushes alot of air in and out depending on setup. It has everything to do with ambient. More fans wont do anything past a certain point.

300cfm sez I know what I'm talking about. Want cooler temps? Install a rad or water cooling, peltier, phase or stick it in a freezer heh. Or wait for winter and Keepit outside

My box is right next to a window 2 feet away so it gets plenty cold air lol

My rig has a few so I can say much. 4 120's and a 200mm all variable speed.

There's also a spot for another 120mm on the door but...a V8 disagrees with that. So I get more than ample aiflowage for the cpu ( low30's) and 4870(~40). Temps are good.

My next case will more than likely be a twelve hundred. Room for gear and double as a spare bedroom.