Depends on the resolution. The lower the resolution the more CPU power is needed. If you will be playing on 1900x 1200 (I hope I`m correct) a game that requires a good GPU you will get a bottleneck, but a smaller one than having the game on 1280x1024.
I think it would be like a 5 to 20 fps drop when , but you should be fine. The game will still be playable. Just lower the settings a little bit and save the money for a new CPU.