2 770s.... I currently have 2x EVGA GTX 770 SC ACX in SLI and it out performs 1 780ti across the board.
HOWEVER..... if you are only running 1 monitor (1920 x 1080) it maybe worth getting the 780ti now and adding another later down the road when you feel like you need the extra performance.
I have 4 monitors and run in 5760 x 1080 in a lot of games which is why I chose 2 x 770s because I wanted the added VRam
Yeah i was gonna run at least two monitor and my power supply supports Sli. 780 didn't seem to be worth it from the price to performance radio but i'm no genius in this area since i wanted the 4Gig 770s