^+1 for nerrawg
Yea, please don't go with that q6600, those days are over. There are way more valuable and efficient quad cores to be had these days, like, you said it, the phenom II X4, or even the core 2 quad Q9000 lines.
Simply put, under any budget, if you want value and efficiency, amd is the way to go, for now at least. And the phenom II X3 is truly the sweet spot.