If you've still got the 4870 lying around plug it in and see how BFBC2 performs with it + 2500k? You can't compare when you more than doubled your graphics processing power as well.
Whose up for doing some q6600 vs 2500k bc2 benchmarks?! Pref with a gtx460 installed. That would help me out a treat!
This thread might help you, the OP exchanged his Q9650 with a 2500K and doubled his BC2 performance, considering it's a great jump from the Q6600 you could potentially see massive performance gains. http://www.overclock.net/intel-cpus/963986-pics-bc2-very-large-gains-i5.html
interesting points raised. Thankyou all. I wont be upgrading - The cash I had burning in my pocket will be saved for a near-future full upgrade instead (i5/new mobo + ram) Bit-tech's communit proving themselves again.
This appeared on Tomshardware recently, and should answer this question nicely I'm impressed my C2Q is doing so well still And it shows how behind AMD really is.