Hello... thx... 1) you have plenty of Ram slots... are you using a 32 bit OS version? or only 1GB sticks?
2) You have a 130watt CPU that uses +12vdc too from the PS.
3) you have a gen 2 PCI-e spec MB.
this is a website/list I look at for general performance comparisons...
http://www.videocardbenchmark.net/high_end_gpus.html
Can you post a website of where you want to purchase the video Card from AND $$$ you want to spend?