Mw3 you will probably near Max out, its the same rehashed engine from the last 4 cod games. Bf3 might be more of a struggle but it depends what frame rate your happy with
I'm ideally wanting 60-80 fps no aa or af medium settings will do me.
Quad Amd @ 3.4 should be ok. I'll look st ivy next year and a gtx570.
Edit: I game at 1680*1050.