Yeah you have a CPU which is at 3.2GHz stock.. so you should have no problems at 4GHz on air. We're talking of a 1.4GHz OC here on a Q6600, and potentially a 1.6GHz OC. Your little 800MHz doesn't spec up for the extra.. 900% (£900) of the price!
I have done it once on P5k-E WIFI mobo but it was not stable. I have seen a guy ho did get it stable and it was in his pc case ont like all thso guys ho has to take it out of case just to cool it down.