The GPU in that PC is crap, the 6850 would be a worth investment. Or you can build it yourself and save money/get better components. BTW, what resolution do you play at? The 460 768mb might be enough...
thumbs up on that one the gpu is disgusting and with that money i would rather build a comp my self!
and yes the 6850 is a good investment and try getting two of them and x-fire it