Definitely ditch the psu, cheap ones can kill the rest of your computer. If you want to sli 650 ti boosts I would reccomend a 650 watt or higher power supply. Good brands are Corsair, XFX, Antec, and the best of all Seasonic. Some individual power supplies from other brands are good also.
As far as a motherboard the one MaXimus linked is good, another option is
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128509
It all matters on your budget and where you live, (prices vary across the Atlantic).