The Xeon X32x0's are in fact Kentsfield chips. They likely are binned better, however I tend to find that the quad core chips are thermally limited pretty quickly. So I suspect the premium of a Xeon X3220 isnt really worthwhile over that of a Q6600. The only benefit at the moment of the Xeon X32x0's is that you could buy a lower multiplier chip for cheaper than a Q6600 (X3210), and likely hit similar overclocks assuming you aren't board limited.