[MetalheadGautham]

Several benchmarks show that RV770 series cards perform BEST only at higher resolutions. A good example is the 9800GTX+ vs HD4850 battle. The former pwns the later at resolutions upto 1280x1024, and sometimes also at 1440x900, but above that, HD4850 starts to rule.

That would mean that at the resolutions you want to game, nVidia is a better choice.
At 6K to 6.5K with great overclockability would be an ideal buy.