You sold one of the fastest cards out there except GTX980 (970 would be only a slight upgrade, and with lower power consumption). So there is your answer.
so don't sell it then is that what you mean how much longer will a gtx 780 last lol
Old thread and such, but....... You sold a card that is just slightly (10 fps max) worse than a GTX 970. After that, you'll be more satisfied in terms of performance with the GTX 980, but that doesn't come cheap..... Maybe wait for the new AMD R9 3XX series launch, and see what it brings for the 400$ price point.