If gaming is all you do then really the price to performance would be better offset by grabbing an i5-4690K and putting the rest of the money into a video card. Even with a good amount of multi-tasking the 4690K will hold up well - I only recently upgraded from my old i5-2500K to the rig in my signature because the software I am currently writing required me to. On the older sandy bridge i5-2500K I was able to play Farcry 4 maxed out at 1080p, have several excel windows with thousands to tens of thousands of cells open, a couple of programming IDEs and very large word documents (300+ pages) with no problems. Oh, and a typical load of 20 ish Firefox tabs.
If this sounds like more than what you do (probably is) then the i5 will be fine. Take the savings from not getting the i7-6700K, DDR4, Z170 board, etc. and get a 980 or 980Ti. The Devil's Canyon chips will be viable to max out pretty much anything at 1080p for at least another 3-4 years.
If you REALLY want the Z170 chipset and the new USB 3.1 features, etc. then the i5-6600K is the budget sweet spot.