BMC offers PC building advice, you can check it out over here.
Recently, I wrote an op-ed piece here titled "The Fast Enough Computer". I argued that for gamers, low- to mid-range components provided the most bang for the buck and could readily play most modern games. The metric I used was "30 frames per second at 1680x1050". In this follow-up, I build a system based on the components I thought would be adequate and test the result with several modern games.