The Phenoms (9500, 9600) are actually around 10% slower than Intel's Q6600, even though the archtecture is theoretically superieur but they are priced according to this. The The new B3 stepping Phenoms will be available soon, they will have higher clock speeds and be better performing:
http://www.xbitlabs.com/articles/cpu/display/phenom-x4-9850.html
The Phenom 9850 X4 will be priced at the same level as the Q6600. But if you have always had a soft spot for AMD, that's good because AMD are in need of their fans right now.
Compare two HD 3870s and two 8800GTs. In a single card setup, the 8800GT is the better performing card, but when the multi-GPU setups, Crossfire generally scales better than SLI, so two HD 3870s will give the same performance as two 8800GTs.