Low VID is the way to go!
I sold my old Q6600 VID 1.2850v to buy the new Q9450 but gave up due to no substancial add in performance from what I was running the Q6600(@4050Mhz with 1.5v).
So I decided to buy a new Q6600 with low VID and I got this batch: L745A793! The VID on this batch is 1.2125v.
It's amazing so far, my DFI X38-TR2 used only 1.20v on Auto vcore option to run the Q6600 at stock speeds (the high VID one used 1.32v).
I have everything in auto so far and going to start overclocking this new baby.
Also it's running Prime95 3600Mhz (9x400) with 1.25vcore, 1.23Nb and 1.21Vtt :up: Impressive compared to my old Q6600.
So the best thing to do if you wanna get a Q6600 these days is to scout for low VID voltage.