I think I am going to treat myself to a RTX 2080Ti but want to know should I also upgrade my CPU and PSU. Specs here. GA-Z170-Gaming K3/I5 6600K @ 4.6Ghz/Avexir Core Blue Series 16GB /AXP 200 Muscle /Gigabyte FE 1080/500Gb/ Samsung 256Gb M.2/OCZ TR150 SSD/2 x 256Gb SSD/ 2TB HDD/ SST-ST60F-P PSU/
None of those would be any issue with the 2080Ti. 600W is more than sufficient power for the whole rig, and the 6600k is not going to bottleneck any game. For gaming, any upgrade (which would be CPU + motherboard, and +RAM if switching to RyZen) would not provide appreciable performance gain for the cost of swap. If you're intending to use it for more than gaming, and the applications you intend to use benefit from more cores rather than faster cores, then a CPU upgrade may be useful.