Agreed with roadrunner, if you choose the q9550 I'd look into the i7, unless money is an issue. If you cant afford the i7, I'd go for the q6600, 10% for $100 doesnt seem worth it
I agree with roadrunner also. However, if your not rebuilding the whole computer and therefore not spending the money for i7, then what do you mainly use your computer for?
then if your sticking with lga 775 go with an e8600 (for the overclock headroom) or get an e8500 and save $100. build out the rest and save for an i7. But you could always get an i7....