CPU advice

Hi all, i need a little help figuring out what CPU to buy for my new system; I'm finally putting on my big boy pants (after copious saving) and going into 4k gaming.

After many years my severely overclocked 8350 had given out and I'm wondering what CPU to get RAM, storage GPU etc. is all sorted. This is going to be a purely gaming pc, no streaming no content creation just face melting (hopefully) 4k gameplay.

After dicking around for a while doing some research I'm thinking the 7700k (disregarding the i9 stuff because it sets off my B.S detector something fierce) or Ryzen 1800x, my conundrum is i know that the 7700 does better in single threaded applications but there's talk of multithreaed performance becoming increasingly relevant of which the 1800x is better, so my question is this. What would you buy, or are there better alternatives?