get the 780 SLI - it will be ~90% of the performance of the titan for a lot less money.NVIDIA GeForce GTX 780 SLI Video Card Review
Out of five games, only two games resulted in a higher playable setting on GeForce GTX TITAN SLI versus GeForce GTX 780 SLI. One game was Hitman: Absolution where VRAM capacity is a real issue. We were able to run at 4X MSAA on GeForce GTX TITAN, whereas we had to run at 2X MSAA on GeForce GTX 780 SLI. It was only because GTX TITAN had more VRAM in an VRAM sensitive game. The other game was Metro: Last Light, we were able to have PhysX enabled with TITAN SLI at 5760x1200 with the highest in-game settings.
Outside of those playable differences, we only experienced small percentage differences in raw performance between GTX TITAN SLI and GTX 780 SLI. At most, we saw a 10% performance difference. Most of the time it was a smaller 8% to 6% performance difference. With performance differences being that small, it resulted in us being unable to raise any settings on TITAN SLI over GTX 780 SLI. It just wasn't enough of a performance boost with TITAN SLI to outshine GTX 780 SLI, especially given the price.
also, i doubt there is good reason to wait since hawaii's die size won't be enough to make the performance anything to force nvidia to drop prices of the GK110 ( 780 - titan ) - atleast according to the local "experts" here [VC] AMD Hawaii is 30% smaller than Kepler GK110