The Q6600, even if its the worst OCer they ever maed will kick but big time on a good MB.
Most Q6600 will do about 3400MHz and up, both of mine hit near 3900MHz with out much time invested in the OC and I had not experence in OCing the newer Intel systems. The typical 24/7 OCs are in the 34-3600MHz range.
In genera;, the CPU "VID" spec is a good indicator of its OCing potential and both mine are 1.2625v VID. Core Temp will give up the VID and the 1.26ish and below should OC very well.
You will need an aftermarket HSF to keep that Q6600 cool to get the high OCs though.
What MB you say.
What budget I say?
My DFI P35 Dark and P38 Dark OC very well
There are many great OCing socket 775 MBs for that Q6600.