Should be a 'slam dunk' to run the PhII 925 at 14x240MHz and bring the IMC/NB to 2400MHz. With good air (and mobo) you will zoom past that.
A Phenom is a Phenom is a Phenom. I guess it depends on where you want to be at the 'high end'. You will certainly be approaching the 4GHz range with the 955 versus 3.5-3.7GHz with the 925.
The 'bottom line' will also depend upon your gaming setup --- the higher you go will your resolution, the greater the emphasis on the video card.
With this
PhII 925 combo you could toss in an HD5770, HD & optical and be off and running for $600.