I have two 780ti cards in SLI, they hold their own - they still run most games at 1440 with good detail at a reasonable speed (Though, they are paired with an 8700K). If I had to buy a new card now I wouldn't get one again though.
Like most people are saying before this post, I'd definitely go for something newer, especially with more RAM because I'm somewhat limited with the 3GB that each one has (Still only 3GB total in SLI).