Well...
SLI GTX 780s: Won't scale as well in higher resolutions, such as 1440p and 1600p. Basically means: You will get better performance with them, but it's not worth the money for the extra performance. Also, consider waiting for the GTX 790. It's basically 2x GTX 780s.
GTX 780 Ti: CHEAPER; Will still max out every game at 1440p/1600p. Again, with this kind of money, it may be worth getting just a GTX 790 for the best of both worlds.
Just so you know, unless something has changed, you can't play games on 2 1080p monitors, either 1 or 3, and I think MAYBE 5. I'd get a nice, 1440p/1600p/4k monitor, as the cards you're looking at are more than enough for that resolution.
Another thing to know, you may be bottlenecked by the small 3 GB of VRAM on the cards above at those high resolutions. I'm not saying now or very soon, but you can count on it in a few years. If you don't want to upgrade for a while, consider either 2x R9 290s or 2x R9 290xs in Crossfire, or if you really like NVidia (like me) a GTX Titan.