My sole reason for posting was to prevent people from being misled by the "easy 4.0GHz" comment as that's way above normal expectations for full stability on air.
At Tom's, we have averaged over 3.7GHz for our samples (3.6 - 3.95), but none to my knowledge have been stable at 4.0GHz on air. The X2 550BE went the highest, the X4 965BE was only stable at 3.8GHz. Of the three I personally tested, 3.67GHz (X3 720BE), 3.74GHz (X3 710) , and 3.8GHz (X4 940) were the stable limits. I have three others sitting here I've yet to test.
Concerning E0 stepping C2D... IMO you have as good a shot of reaching a stable air-cooled 4.5GHz on an e8600 as 4.0GHz on a Phenom II, so no doubt which will reach 4.0GHz easier. Shoot, even the E5200's I've tested are batting 80% on air in 4.0GHz stability.