I would definitely recommend the i5 4690K if you don't mind.
I'm generally of the same opinion as Mkenyon, I don't really recommend SLI unless you're running 4K monitors or other similar situations where even the most powerful single graphics card won't cut it and you're forced to go with two cards. Not all games support SLI and not all of them scale well, so doubling down on the GTX 970 doesn't guarantee double the performance.
A single GTX 970 is still your best bet for price-to-performance. With some tweaking,
you could overclock the GTX 970 and end up with performance quite close to a stock GTX 980, although specific performance figures will vary by the game. Of course the GTX 980 can also be overclocked, but doesn't quite offer the same bang-for-buck.
The single GTX 970 should do you just fine for now, it will be capable of handling very high if not maxed settings adequately in most games. I'd wait to see how AMD's R9 3XX line (rumored for June launch) and the GTX 980 Ti turn out before deciding to get a stronger graphics card or not.