I did a whole lotta testing to see which worked best. I recently installed a Thermalright SI-120 heatsink with a 120mm fan. I also have a 120mm at the front bottom to suck air in, and a 120mm at the rear top sucking air out. There is an additional 80mm on the side blowing air onto the CPU fan. With all the combinations, I had lowest temps with the side fan blowing down onto the CPU fan, and the CPU fan blowing down also. You would thin (because of the SI-120 design) that this would increase the temps...but due to the panaflo volumes (CFM) it cools a lot better
. I have a fairly warm room and the airflow around my PC is pretty poor, but with this combo, I have about 35-36°C on idle and 50-55°C at full load.
With graphics, I used to have a standard fan (PCI-x ATI X800GTO 256MB) but it kept overheating. I installed an ArcticCool AT4 which does the trick. They are also the new standard for the X1900 series etc (I think). The trick seems to be blowing air OVER the heatsinks on the card, and then out through a grill at the back (which came with the fan).
Also, here is the discussion I had a while ago on the same topic......http://www.bleepingcomputer.com/forums/ind...29&hl=suck+blow
Hope that helps!!!