I believe the GTX 780TI would be more than able to handle 2 screens at 1080p as long as your only gaming on one screen. From what iv seen of the card as long as your not using both screens for heavily graphical intensive purposes at the same time, you should see very little impact on gaming. You should be able to consistently sit on about 60 FPS while gaming.
Here is some reviews on the subject: http://www.mmo-champion.com/threads/1531747-GTX-780-Ti-Dual-monitor-worthy?p=27507205http://www.tomshardware.com/answers/id-1874549/single-gtx-780ti-run-1920x1080p-monitors.html
I wouldnt expect TO much out of the card, but it is considered a good card and as long as you dont plan on Ultra for every single modern game that comes out while using 2 screens at 1080p, you should be fine, especially if running games just on high.