What case are you using to house the q6600 cpu,
As you may well know the q6600 is really 2x e6600 chips on one die so heat is doubled.
You may not want to stay at 3.2 and try for 3.6 with obvious heat output increase.
So I would go for the Noctua nh-d14 which I run on my Q6600 in an Antec 902.
But hell make absolutely sure it will fit in YOUR case before you buy.
That,s only my own opinion it really is case dependant with these larger hsf,s on the market today.
well, why dont you go ahead and buy a coolermaster hyper 212 ) cooler..its cheaper and the really good in terms of price and performance,before you do that 'd listen to oshimaida regarding the PC case size