Intel's s1150 and AMD CPUs and motherboards are only compatible with DDR3 memory. You have to go with Intel and its socket i7-5xx0 processors from the 2011v3 socket to use DDR4 and a few months ago there was an user here that downgraded from the new i7-5xx0 to the old s.2011 i7-4xx0 because DDR4 was slower in games.
You'll be better with a high end s1150 processor with the fastest RAM you can find.
2 980 in SLI are faster than a Titan X, which is almost but not quite enough to game at 4K at 60fps and it will only get worse as new and more demanding games like The Witcher 3 are launched.
I'd go with at least a good 850W PSU. Corsair, SilverStone, Seasonic are good brands.
As for SLI, I've never used it (I prefer to go with a single card to avoid those kind of problems), but you'll need to use two identical cards from the same brand to make it work.
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.
