Go for the 955 and the 4870 and you can play anything maxed too. I cant believe someone actually said get a less CPU and a bigger GPU and you will be all set. I have a VERY similar rig to the one you listed and I can play any game MAXED on 1680 x 1050.
The x3 720 is also a great chip and won't do ya wrong but with the price difference you are paying for that you might as well go with the 955.
The 4870 1gb is a sweet card and will play ANYTHING you throw at it as well. Sure you might not get 60 FPS on Crysis but you will get decent enough FPS on MAX settings to play through the game with no Hiccups.
If you are looking to shave a few bucks off you could go with the x3 720 but if you are looking for a good deal on a rig that deal you got there isn't a bad deal at all especially for a prebuilt rig with a 955. Considering the 955 is 245 dollars on its own and then a 4870 1gb is around 200 bucks as well. So you figure in the rest, shipping, and the fact that you get a WARRANTY with your rig that you wouldnt get by building yourself (even though you said you dont want to) and you got yourself a good deal there.
I would go for it....