https://ark.intel.com/products/codename/97787/Coffee-Lake
The i7-8600K is a 6-core, overclockable CPU that costs the same as the i7-7700K. It doesn't have hyperthreading so it's 6C/6T but that's better than a 4-core CPU with hyperthreading (4C/8T).
(The i7-8700K is hard to recommend unless budget is hardly an issue. It may be difficult, even streaming + gaming to utilize the hyperthreading as SIX really fast cores already go a long way... I believe it's roughly $420 vs $280 so an extra $140 and possibly an even better CPU cooler than you'd get for the i7-8600K)
There's a lot to like about RYZEN, especially with AM4 socket hanging around a while (potential Zen2 8-core later, and easy to replace motherboard after Warranty).
There have been issues getting DDR4 memory working at full speed (some stuck as low as 2133MHz). Not really sure how much of an issue that is currently but I'm still helping people out unsuccessfully at times.
*however, if 1080p, high FPS gaming is a priority then go with Intel's Coffee Lake. In some situations it can get as much as 50% higher FPS vs Ryzen. (at 5GHz and in some games only)
I wouldn't personally run Coffee Lake at 5GHz myself, I'd probably get a good AIR cooler (I dislike liquid coolers) then overclock as high as I can reasonably go with temp/noise constraints so maybe closer to 4.6GHz but that's just me.
At "only" 4.6GHz (all cores) you can as high as 40% more FPS in some situations vs Ryzen. It's much smaller at 1440p.