Just finished a budget AMD build and spent around $350:
AMD Phenom II X2 555 Black 3.8ghz Slight OC (hopefully unlock third or fourth core)
4gb Corsair Xms3 (2x2) Ram
Coolermaster 430 Elite Black Case
MSI 870-G45 Motherboard
Thermaltake Tr2 430 Watt PSU
Nvidia Geforce 7900GTX - ITS ABOUT TIME FOR AN UPGRADE
With a Gpu budget around $110-$150 i was looking for a decent mid Nvidia card like the EVGA GeForce GTS 450 1GB
In all honesty I'd rather stay away from ATI cards but all suggestions will be read.
I play all my games on 1280x1024 resolution, i have no problems with games like Css, Dod:s, Modern Warfare 2, or WoW at full settings this card is more for Black-ops and when i buy it BFBC2.
Keep in mind I will be spending another $50-$90 On a New Antec or Corsair power supply around 600 watts.
TLDR: Suggestions on a new Gfx card around $150