|Just about anything is better than onboard video, but decent standard PCI cards for gaming are few & far between, not to mention relatively expensive. You are asking about standard PCI & not PCI-express, right?|
Try to find a card with 256MB memory & a 128-bit memory interface. Avoid 64-bit memory if at all possible. Here's a 9400GT PCI card with 512MB/128-bit memory, but it's $75:
You *may* be able to find an FX5500 w/256MB 128-bit memory, but I'm not gonna do the googling for you.
The FX5200 256MB/128-bit is another possibility, but it's not as good as the FX5500...here's one for $41 +shipping:
Stay away from the MX4000 & Radeon 9250.