It's really hard to recommend a good gaming PC, as some people have higher standards than others. Take me for example, I'm a hardcore PC gamer, so recommend parts that would chose, regardless of price, where another person would consider price first and performance second.
That said, it goes in order; Processor, Video Card, Amount / Type of Ram, Power Supply.
AS for that PC, while its nice, the video card is lacking for gaming and it offeres DDR3, which is wasted on a Quad2core. You won't see a huge difference between DDR2 and DDR3. Change the memory down to DD2 and the video card to either the ATI 4870 or GTX280/GTX280 and you'll have a gaming beast on your hands and will be able to play Crysis, Crysis Warhead and any new game coming down the pipe.
Keith Mitchell, Server Engineer, Hostmysite.com