as everyone else is saying 920 is the way to go.
If your wanting a lot of power and and fairly decant price for a cpu the 920 will be it. They my be both quad cores but with the Hyper-threading it make the cpu act like 8 cores instead of the true 4 cores.
The core 2 quads does not have the Hyper-threading.
I still have a Intel P4 2.8 GHz computer thats about 4 or 5 years old and still runs very good. It's so good that it can play assassin's creed which requires 2.2ghz core 2 duo. I believe it is only able to play it because of that Hyper-threading.
So in the long run, it more worth getting the I7.