Just to explain my point earlier before, when i say 970 = 780Ti that's based off overclocking benchmarks where many 970s and 780Tis can be overclocked to reach about a stock GTX 980, and an overclocked 980 (Strix, MSI gaming and Gigabyte G1 are best for this so far) exceeds the 780Ti on every single benchmark i've seen while also being more power and thermally efficient. so i definitely agree for future games, and even current and past games the 980 is way better choice than the old 780Tis
if you're going with a 980 SLI that's really good to push the highest frame rates on that montior, i think i know which one you have, same as me, he ROG Swift. a single 980 or a single 780TI is okay for it but you really need a 980 sli to push those high frame rates that beast of a monitor is capable of, i approve of a 980 SLI highly.
you should be extremely happy with the 980s, they're brilliant cards
Especially since two of them can push that 144fps on ultra in ALMOST every game, excpetions being ones like battlefield 4, crysis 3 and such