i recently got 2 case fans to cool my system as the CPU was exceeding 70 degrees celcius in temp. i was just wondering what the best configuration would be for optimal airflow. below is a diagram of the rear of my case

---------------
|xxxxxxxxxxxxx| <-----fixed psu fan
|xxxxxxxxxxxxx| (out only)
|--------------
|xxxxx| |
|xxxxx| <-----System fan1 (out/in)
|xxxxx| | (currently IN)
|-----| |
|xxxxx| <-----System fan2 (out/in)
|xxxxx| | (currently OUT)
|xxxxx| |
|----- |
|xxxxxx <-----vIDEO cARD
| |
| |
| |
---------------

any suggestions are appreciated

That's weird, your video card is below both system fans? Is there a spot for a fan at the front bottom of the case?

The fan placements at the back should be blowing out of the case and the ones at the front/side should blow into the case. Fans higher up should blow out and fans near the bottom should blow in. You should try to have equal intake/outtake fans.

So it goes like this: cold air blows in at the bottom, air heats up, air rises upwards, air is blown out.

Maybe try and put an intake fan on your side panel. Cut a hole (side panel opposite cpu) where the fan would be perpendicular with the cpu. If you've alligned it just right your cpu will be getting cool outside air from the side fan. Another note..you can also create a funnel to direct the airflow directly to the HSF. Basically, what this does is prevent the HSF from bringing in both hot inside air and cold outside air at the same time. It will thus bring only the outside air into the HSF. The funnel should roughtly sit maybe a 1/4" from the HSF. Hope this helps. Another good thing is using a high quality HSF. I recommend a Thermaltake Volcano 9. Good Luck solving your heat issue!