that's a decent build. Your PSU is fine. The upgrade is a decent one, although some would say you need to jump two tiers on the CPU, it's not hard and fast. The 7700k is a great gaming chip and offers the highest FPS. If you went with a Ryzen 1600/1700/x, you could get similar gaming performance with better performance in every other multicore test. You would save a few quid. Then you could get a GTX1080/ti, and have a much better experience, and more FPS to boot!