I am still using Q6600 @3GHz +HD6850 and I am still not planning to go for upgrade this year.
I am now playing:
- Starcraft 2 + hear of swarm
- Mass effect 3
- Tropico 4
- Skyrim
- Torchlight 2
Now, for your case. Q6700 should not that different to Q6600. I say keep it if you already have it.
Q6700 is a true quadcore.
Try OC it if you like.
About the GTX650, I would go at least with HD7850 if I were you.