Here are the 770s vs the 780 ti.
http://www.game-debate.com/gpu/index.php?gid=1920&gid2=1824&compare=geforce-gtx-780-ti-vs-geforce-gtx-770-sli
770's vs 760's
http://www.game-debate.com/gpu/index.php?gid=1824&gid2=1823&compare=geforce-gtx-770-sli-vs-geforce-gtx-760-sli
The cheapest you could get a 780 ti is $670. The 770's would be $630. And the 760's would be $472.
The 760's have the best performance for the price. Then the 780 ti. Then the 770's.
These are the websites I used to come to this conclusion.
Scoring system:
http://videocardbenchmark.net/high_end_gpus.html
Comparison: www.game-debate.com
Prices: www.pcpartpicker.com
So to come to the conclusion, I had to first divide the score by the dollars it cost. So the 780 ti was 13 points per dollar. For the 770's I had to compare a normal 770 and the two 770 side by side. Game debate said the SLI was 30% better. So I found the score of the 770 and multiplied it by 1.3. And I then divided the score by the price and it was 12.8 points per dollar. Same thing for that I did with the 770's I did with the 760's. And the score was 15 points per dollar.
So since all I care about in gaming is a smooth FPS. And since the 760's could get some high FPS on games, I would just go with them.