I don't know, but I for one, think that Q6600 was the best CPU ever made. It came out in 2007 and 3 years later it just became even a better performer. It's exactly like the wine, the more time passes the tastier it gets. I don't remember a CPU that resisted so long, being able to stand in the performance league, after 3 years of its release.
It's very resilient, you can't brake it, you can't burn it and it overclocks like crazy, without killing the motherboard or ram. It holds any videocard from the last generation, once you crank up its clock, in any resolution or game.
So, yes, I vote for Q6600, just because you'll get it cheaper and frankly it doesn't matter that it's used, because nothing will bring it down.