Yeah, you don't need tri-SLI for all that crap. For a PSU in the case of grabbing 2x 260's, grab either the 750w or 850w Corsair. Either will suffice just fine. If you don't mind spending the extra moolah, grab the 850.
EDIT: By the way, you would be more than fine with a tri-monitor setup, you don't really need 4...especially if they are 22" or above. I'll be doing the same thing when I get the money.