Case Cooling for Chepo case. PCI Slot cooler vs Case Mod

Hi Guys,

Just bought a sapphire 5770 and it was getting around 57 degrees Celsius at idle, not sure if this is usual since i read it should be around 40 degrees so i figured that it must be the case airflow. I mounted a 120mm intake fan on the front lower part of the case. This reduced the temps to 47 degrees. still not that satisfied with the cooling so i planned to add another exhaust for the hot air the GPU was blowing down. so... do i go with a PCI slot cooler or do i go DIY and drill some holes on the side of my case around where the GPU is mounted and then put in a 120mm exhaust fan.

My system is in a mid atx cheap case and my current cooling is 1 x 120mm intake on the front, 1 x 120mm exhaust on the top side of the case, and the 1 x 120mm PSU exhaust fan.