I'm sure as you know the gtx 780 is a "nerfed" titan while the gtx 770 is a higher clocked gtx 680. The gtx 760 ti will be a gtx 670 rebranded and won't be released until August most likely.
My advice if you plan on purchasing a new video card is to wait for the 700 series to come out and the 600 series drops in price. You WILL get more performance per dollar once the 700 series comes out.
the 7xx linup is basically a refresh of the 6xx linup. same chip architecture, same basic design.
the 760ti would be roughly equivalent to a 670~ not a 660ti. (imagine everything in the 6xx linup shifts down a 10's spot number in the 7xx linup to make room for the gimped titan that they're rebranding as a 780). The reason the 780 looks like a titan is because it's a gimped titan (they're crippling part of the titan to make the new the 780). The 770 will be a rebranded 680.
that said nvidia is talking about a 10%-20% price hike in the 700 series across the board.