Yes two 780s will work, but two 290s would work better and come out a good bit cheaper. What parts do you have already?
16 GB ddr3 1866 ram
MSI G95 Z87 Gaming Mobo
Samsung 840 Evo 120 GB SSD (Boot Drive)
1 TB Seagate barracuda HDD
850 Watt Antec Power supply
i7 4770k (I changed my mind, i want the option to over clock my cpu)
CM Strorm Trooper case full tower