Woah, that is one sexy case Wayne my friend. Cooling:
Front for intake
Rear for exhaust
Side for intake (like has been said)
A good ratio would be 50/50. For every fan intake, you should have one exhaust. If you have eight fans, 4 should be intake and 4 should be exhaust. Just an example. However, every combination of parts is different. Every machine is different. For the typical person, the intake on the side is what is needed. So that is why they did it like that, it is the most practical application. But, like I said, everyones machine is different. What works great for someone may not work great for someone else. The best way is to experiment. Most likely intake is the best, but who knows, maybe exhaust will prove to be most effective. Experiment, find out firsthand which works better, and report your findings.
I sould like a damn 7th grade science teacher...