Psycho's chart is better but I'm not sure I believe that fully either. A single x2 takes 486W at load. Not a problem there. Toss in another 300W max TDP card however, and you should be just under 800W, not at 836W. A single x2 is 350W?
As for the other guys list, its more or less BS. 70A for 295 x2 setup? Its funnier the lower you go. GT430 (fermi card here) needing less power then the GT220? The GT220 needing a 30A PSU? (btw, 30A x 12V = 360W, but you only need a 350? Math doesn't work out for the GT240 either.) GT240 needs more power then GTS250? Someone has some funny (and wrong) ideas about power.
Considering the returns on quad SLI, I wouldn't go for this. Get the GTX580 or 570. Should perform similarly, but with no SLI issues. Probably less power as well. Toss in DX11 and there isn't much reason to go the GTX295 route.