I think G92 8800GTS is the best bet for that money. The only problem I see is your cpu, it is most likely that your rig won't be able to take full advantage of lates GPU such as 8800GT/GTS if it can't run at 3.0G abd above.
Maybe somethings like this.
E2180 OEM $60
Gigabyte P31 $66
2GB Ballistix 667 (good OC) $19
Or get 5000+BE if your board supports it.