P.S wasn't there something... like... you need a special Mainboard if you want to change multiplier?
Yes. P67 or Z68. H67/Q67 won't let you change multis, IIRC.
Intel have, in Sandy Bridge, a more efficient architecture than AMD with the Phenom II. That said, the Phenom II is no slouch - frankly, unless you're pushing the bleeding edge of overclocking, or are doing a lot of video encoding, you are unlikely to notice a great deal of difference.
I singularly fail to see much difference gaming on my Core i7 rig at 1920x1200 and my Phenom II rig at 1920x1080... but all is not equal in the GPU front there: the i7 box has (on paper) a significant advantage in terms of CPU, being OC'd to 3.8/4GHz (depending on how I'm feeling) above the Phenom II at 3.2GHz... but the i7 system has GTX460SLI as against GTX470SLI. Having said that, the 460s are OC'd to pretty much match the 470s in terms of performance, and have more VRAM. Nevertheless, unless I'm
actually looking for a framerate difference, I can't honestly spot one. I guess I'd see a difference if I ran framerate counters all the time... but I don't. As long as the game is smooth and playable, I'm happy.