I'm personally not a fan of Nvidia products after their most recent generation. I've converted to an ATI kind-of-guy and i've been extremely pleased. I'll suggest the ATI 9800 Pro, but it that's outside of your budget go with the 9600 or 9700...
[quote="[GDC]_Polemarcus":c8284]I've converted to an ATI kind-of-guy and i've been extremely pleased.[/quote:c8284]
Agreed. I've had an ATI 9700 Pro since it's release and it kicks ass. I've been able to set all the graphic options to the max on every game I've tried since I bought it. Two thumbs up.
Disclaimer: I know my CPU and RAM also need to be taken into account when determining my PC's capabilities.
If your really looking for a good method to search for a video card that will best suite your system go to http://www.futuremark.com and download the free version of 3dmark 2003. You will be able to benchmark your system, then you can use their online database to compare and contrast other cards and how they might perform in your system.