actually, this game is pretty CPU intensive. the sound is all off the CPU for BC2. but yeah, depending on your OS, your current CPU may be ok for around 20-25+ FPS with the current GPU you have. given that, and you should be able to play decently with the right settings. oh and manually making the game run on DX9 should help quite a bit.
i went from a 3.0 GHz X2 to a 3.0 GHz X4 and went from 30 FPS to 85 FPS with the rest of the parts being the exact same. if you can, try to save for a C2Q.