have a friend who has a E6400 overclocked to 2.8ghz with 4gb ram and currently has a 7900gtx. He wants to upgrade his video card and looking for $150 or less (new/use) card. He will be cpu limited so not sure what's the best card to upgrade to. Will be playing BC and Modern Warfare @ 1600x1200. Will a 4850 or 260gtx be overkill without getting a CPU upgrade?