You dont need a fancy case for good airflow. I have possibly the cheapest, flimsiest, POS case in existince, but with 1 120mm in the front, 2 80mm in the back, and a fan controller to pump em up a little, my ambient temps inside the chassis kick ***.
EDIT: Not to say that side fans and blowholes dont help, they do.. but they arent essential, IMO
-DFI Lanparty NF4 Ultra-D
-AMD 64 3000 Winnie
-eVga 6600GT (PCIe)
-Mushkin Dual Pack PC3200 (512 X2)
-80gb WD SATA HDD
-Creative Live! Series 5.1 surround sound w/subwoofer