HD 6950 is able to get you a very playable FPS @ ultra 1080P, with your current CPU it won't make a difference compared to a Phenom II X4, but in other games there' will be a huge difference.
So right now, you can play BF3 without no problem, you should get 40+ FPS.
But you gotta upgrade that CPU soon. X4 980 BE is the most powerful gaming CPU in the phenom II series.
No it isnt.... the 1100T BE , is...
All the best Brett