That pretty much says it all. Even @3.2ghz an i7 will see nice scaling by adding a second 480. An i7 at that speed isn't as fast as a q9550 @3.8, so obviously having SLI'd 480's with a q9550 is the better option of the two.
I'd rather have an i7 than a q9550, but if the choice is between the 9550 and two 480's or an i7 and a single 480, I'm picking the former every time. It would give a much better gaming experience.