mace200200 :
750w will do two 660's just fine, two 660's will not do 8 monitors though, You'll want to look at 280x's or 770 4GBs but even then I can't say for sure, nobody runs 8 monitors.
Wasn't nvidias support for monitors capped at 3 monitors? (In surround, honestly not sure about non surround but pretty confident in surround it was only 3) (legit question, nto trying to be rude.)
But yes I agree maybe dual 280x's depending on resolution... Oh and that whole, need more ports thing.