Should i get two GTX 470 or one 570GTX?

bump

470 sli is going to be a lot more powerful but draw way more power.

what power outage will i need to cover that?
will 750Watt be suffice?

You may be better off buying the best single card GPU you can with your budget now, and then you'll have the ability to sli in the future(15-18 months) and get a bump in performance. I'd go with a gtx 580, or if you can afford it a 670.

Why not go for something more modern and less power hungry?

GTX 580 = Overpriced.

A GTX 660 Ti would be better then the 580.

umm id say budget
cant afford around 400$ right now
and i can get 2 470 for around 300$
thats why
and i already got a 460GTX but i think its faulty too much freeze and problems with graphics so i want to get something better
but i cant afford too much
already got the new mother board and new CPU
which by itself cost a load

Buy the best single card you can afford then if you need more power SLI afterwards.