The video card is more important than the CPU when it comes to some games, however others are the other way around, but generally, most need a balance of both.
Honestly, you'd be better off going with an i3-2100 than a Phenom 955 anyway. Either way, Sandy Bridge is really the way to go right now, unless you are looking at a really low-budget machine.
A 2500k will future-proof you quite a bit more, can be overclocked like crazy, will give you better performance in games and way more performance in normal applications (especially engineering ones). You won't regret buying one. I bought two haha.http://www.anandtech.com/show/4083/the-sandy-bridge-review-intel-core-i7-2600k-i5-2500k-core-i3-2100-tested/20