as a true gamer, i would say go for the 8600k,
two reasons
1.After a year or two , game will require more cpu power, i see a lot of user. having a i5 non-k cpu (i5 4460, i5 7500/6500) asking what to do with mediocre fps , and unfortunately, most of our response will be sorry CPU bottle necked, nothing you can do, replace mobo+cpu.. where as user having 4690k/6600k, we will say, oc it to 4.5 Ghz it should be good for a while. the OC headroom makes up for 1 generational change in CPU. (GPU gains tends to be more significant)
2.most 1080p gaming are CPU bound, you see a linear gains in fps by pushing the cpu, especially in those single threaded/poorly optimized game (PUBG and WOW).