purpose: my fav games unreal tournament 3; cnc3 tiberium wars should be able to comfortably / normally play at 1680 x 1050
new planned specs
core i7 930 motherboard with in $400 or best suited for my purpose: pls suggest ddr3 kingston 2gb 1333mhz ram
More aboutsuggest graphics
HD 5770 is a good choice,however get a 500+ PSU(Corsair 520W would be good)and also make sure you get 4GB RAM instead of 2GB. And for motherboard,Asus P6X58D Premium would be a good choice
I don't know about unreal tournament 3, but my 9800 GT runs tiberium wars at a constant 30 FPS (this is the frame rate cap), and that is on very high settings and 1440*900 resolution, so it is not that GPU intensive.
^+1 Maziar. If you would like more help picking out all the components, you can always ask over in the Homebuilt section.