I'm using an Optiplex GX620 with a Radeon HD 4350 slapped in.
It's quite fast, though I'm not sure how much it costs.
Things like TF2 and L4D2 can run at max/really high settings with 50 FPS.
The graphics card was like $120, but I got it on sale for $60.
The 4350 sucks complete stuff. I had one in my computer at one point and it could not manage more than 40fps in L4D with
EVERYTHING turned down to minium.
Look on craigslist or in your newspaper to see if anybody is selling computers.
