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I went from 980 sli to a fury, although this was due to buying a freesync monitor, obviously fps are lower but I'm one of those that can't tell the difference between 100 and 60 fps
Just use a single 780 for now if you're really unhappy with sli, As everyone else said new cards are incoming and a 780 isn't exactly a slouch it'll still run anything on the market game wise so spending money on a replacement now is a waste.
It's not that I'm unhappy.
My old i5 750 and P55 chipset need refreshing and thought I'd look at GPU options while I'm at as it seems less and less new games are supporting multi GPU setups (unless I'm wrong!)