You'd notice it in games that don't utilize SLI or at 4k. Other than that, probably not. Most of the reviews for the 1080 so far have it about -10 to -20 fps away from 2 980s in SLI in some games (watch Paul's Hardware review on the 1080). Since 2 780ti's are close I'd say it's only worth it if you need the 8GB of RAM or you just want to use less power. You can always sell your cards and buy a 1080 once the aftermarket ones come out, they will be cheaper than the Founders Edition.