If you're just gaming, I would go with the overclockable i5 8600k(maybe the 9700k but it's within 1%) for pure gaming. Strongest quad and single core action all around, and that translates to better gaming experience on most* games out there. And if space is not a problem, I would grab one more SSD of some kind. That 512 will fill up fast if you're loading windows and your games on it (which you definitely want to do). Also, see if you can find a faster and lower latency ram kit too if you can. Having lower timing for everything your computer does and storing and accessing everything faster is definitely worth it.
(If you're going water cooled, might want to think about overclocking if you want to get every bit of juice out of every game)