yea, i'm going to have to go with Lume on this one, you can't buy a pc for that cheap and expect 100+ fps on new games, my pc parts currently are still worth more than that and i dont even get that high of fps. while overclocked mind you, 4.2ghz amd 965be and gtx 465 at 870mhz core, 2085 memory(on par performance wise of a moderately overclocked gtx 560ti)
i will say this, the 6850 can be highly overclocked but if you're looking in to anything tessellation nvidia or newer ati like the 7000 series is the way to go. 560ti and 570 cards are decent mid to high end cards.