To be honest, any 550W Antec power supply should be able to run that system. Some are better than others, but for the most part Antec is a good and reputable brand so the build quality is generally good to very good. The lowest end Antec 550W would have no problem with that system.
Each game will vary on what graphics setting you can run at. BF3 will probably run at lower settings with your setup. It is a VERY demanding game. You could run at medium with some other settings turned down or off. COD is not that demanding and you would be fine.
Is this system built already or in the process, or it still in planning stages? The reason I ask is I would have suggestions on your other components if possible. Specifically the amount of RAM and CPU. I'd go with 8Gb if possible. The Phenom II CPU's are good, but have been around a while and are being phased out mostly, so I would never buy one new. I'd look at an AMD FX-6300 chip.
I would not worry yourself over it. The Phenom II is still a good chip, and would perform fine in gaming. I just personally would just go with a newer architecture if I was going with a new system. The video card will probably hold you back if anything. The 7850 is a good entry/mid level gaming card so I would expect such performance. I would not expect to sustain 60FPS at 1920x1080 resolution in B3 on Ultra. My GTX580 wouldn't run Ultra. However, it looks good even on Medium. Most games a 7850 would run just fine on modest settings.