Originally Posted by ehume
The coolest air is what comes in from the outside. In a case with two top fans, the forward fan can be set to intake and the rear fan position blocked, to form a wind tunnel effect. People who have converted from top exhaust to top intake generally see a 3-5c improvement in temps.
Air coming from the bottom of the case is warmed by motherboard components, which reduces the cooling power of your heatsink.
The front-to-back airflow can be improved by adding an intake fan in the 5.25 bay.
I also advocate removing the rear grill and rear fan to let air exit the case freely. It's also quieter.
^ This. I was experimenting with adding a little extra fan I had to my front 5.25" bays and boy did that make a difference. My CPU max load temperatures dropped 3-5C in about 5 seconds after I put in the fan. Also this was a little CM 80mm fan I had lying around which only has about 22CFM. So adding a nice 120 or 140mm fan with about 30+ CFM should drop your temperatures quite nicely.
Unfortunately, the same can't be said for the GPU's. I went as far as to even stick my hand halfway through the case from the front while it was running on full load and tried to angle the fan towards the GPU's. It didn't even faze the temperatures of the cards...not even a single degree. That being said though, the fan was right in front of my palm which was blocking quite a bit of air.
But a fan in the front bay and reversing the top exhaust should drop temperatures quite well.