You do NOT need a 980ti for most situations. Yes, I have one, but I intentionally went with overkill. The 970 w/6600k is MORE than sufficient for most people, that right there is enough to put your computer in the top 10%. What games are you playing?
If you want to take every brand new game and insist on cranking every setting to max, go with the 980ti. If you're mostly playing games like WOW, even the 970 is overkill. I will admit I'm happy that I had the 980ti when Arkham Knight was re-released, because it is overkill enough to make the game playable @60fps on my machine.
Are you going to be overclocking and trying to push max settings at 4k? If not then you don't really need any of that stuff.
If you aren't going to overclock you can drop down to like a normal 6600 and save yourself $80 or whatever the difference is... 6600k doesn't have hyper threading like 6700k so the only advantage it has is higher base (irrelevant for the most part) and overclocking... Likewise you wouldn't need an aftermarket cooler (wouldn't hurt, but unnecessary) (also referring to the 6600, you would need one for 6600k since it comes with no stock)... And if you are only going to be trying to max games at like 1080p, a 970 would be enough for most games.
I would also suggest dropping the HDD and going exclusively SSD as HDDs are loud and annoying. If you absolutely need cheap/large storage and don't want to drop the money on SSDs, get an external so you don't have to deal with scans/spins/hangups of an internal just idling on your computer.