Probably consider AMD 7770 in that price range. You might want to consider upgrading your PSU at the same time, since you have probably lost about 30-40% of capacity (due to capacitor aging of 10%/year).
$122 shipped - $15 MIRc = $107SAPPHIRE 100358L Radeon HD 7770 GHz Edition 1GB 128-bit GDDR5 PCI Express 3.0 x16 CrossFireX Support Video Card
PSU minimum upgrade:
Currently $43 shipped.Antec VP-450 450W ATX 12V v2.3 Power Supply
ikas, I don't trust your powersupply, I doubt it even puts out 14amps on a rail.
I agree with luny, get a new powersupply AND a GPU. However, currently the CX430 is on for sale for $25 after rebates, and although the VP450 is a good buy, imo this deal can't be beat. Corsair make pretty good PSU's.
Good choice of GPU though.