You wan't to save money and play at 1920x1200 gaming AA0 AF16 , game details medium to high then get a G92 chip. 8800GT or 9800GT same card same performance. At 1600x900 you can use 2xAA 16AF which is free since x800 6800GT days and game details to high. Youll get blazing performance in MW2 and UT3 engine. The crysis engine will kill you though. GL
You can find these for 80 to 100 dollars, especially on ebay. You won't regret it as long as your CPU is not a bottleneck,, good luck and GB