Theres only a few games out that even make use of quad cores right now. Most are happy on a high clocked dual core. I cant imagine quad cores being incabapble of running games any time soon.
Also, with regards to the x4 955, my friend has one and overclocking is a breeze with the unlocked multiplier, apparently. He just added to the multiplier to get a 3.6ghz speed, which is more than enough!
If not overclocking, I still think the phenom quads will do better, purely due to the higher clock speeds and quad core being more than enough for nearly all new games