Your GPU & CPU setup will perform admirably at 1080p... It will perform quite well at 2K (1440p)... 4K, on the other hand, will require some sacrifices for "good for 4K" performance. Now, if you got 16GB of fast RAM, you're good to go for practically any game.
Your weakest link is the PSU... it is at the very least a part killer... At worst, a unit that can have you shopping for a new roof over your head. Look for a better one, ASAP. Your power draw is about a few watts more than hlaf of your current PSU's labeled power handling/delivery... If its actually working AND delivering clean power, its a miracle... Most of those dirt-cheap power supplies can't deliver more than 1/5 - 1/3 of their rated power without putting anything in danger.
Usual common brands for good to excellent units are: Seasonic, EVGA SuperNova series, Corsair AX?,HX?,TX,RMi... (substitute a letter where there is a "?") There are a few others, but these are a good place to start looking. Get the most expensive one of the suggested that you can afford and is about 550-650W. (My PC w/ the 2600X and a GTX1080 has an est. 369W since both GPU and CPU are a step or two down.... that power level should be plenty with a good PSU.)