I recently bought a Silverstone SG03. I was able to fit a 4870 inside, no problem. The system needs two 120mm fans at the front though (it only comes with one). You want to make the the exhaust system on the GPU (like the one on the Sapphire 4870) puts the air directly out the back. Your PSU should be able to run well under warmer temperatures since ideally you'll want to face the PSU intake fan directly over the CPU. If the PSU is faced away from the CPU (sucking air from outside the case) you affect the positive pressure of the case. If possible, you want to find a mATX board that will mount a Zalman 8700 after market CPU cooler. The board I have won't fit the cooler, but the info on the boxes says it will fit mATX boards.