most midi tower cases are about 5-6 cf, tower cases are about 10-14cf, so with 230cfm going through it a midi would only have the air in it for about 3-5 seconds (the fans don't push as much as they are rated for in normal curcamstances) and about 6-10 seconds in a tower, this doesn't really give it much time to absorb heat, I would say in a midi case any more than 100cfm (200cfm in total) is a waste unless you have been lazy in the placement, and with a tower I would still only have about 150cfm's worth of fans in and out (300cfm) in total, intake for my case is one 31cfm at the bottom front, a 47cfm at the top front and another 30cfm on the side which is 108cfm in total but probabally only works out at about 90cfm in reality, and for exhaust I have 2 30cfm in my psu (like the enermax setup) a 30cfm fan behind the cpu and a 31 cfm behind that but ducted round the cpu which is only 90cfm out but I prefer a little positive pressure, position and the temp of the air is more important than the amount, as if I put my computer on the floor I get temps 3-4oC cooler, this gives me a motherboard temp of 28oC with my cel 900 with 2.2v (burning in)which I can't better even with the case off and the air in the case is only 24oC with a room temp of 25oC (the temp on the floor is only 20oC)
