I would go with GTX 780, although more expensive. You might not get the same performance with SLI that you get with 1 Gtx 780. SLI 760 is on pair with a Titan, a 780 could give you less FPS on some games sure, but you wont have to hassle about SLI, microstutering (although practicly reduced with SLI) and far less heat in case.