500w 80+ psu.
Evga 500-W type psu, not even the 500B.
Dont push it with higher end gpus. With that psu, the best I'd do is a 2070Super or Rx5700 (non XT) as they'll not have the draw and don't have the transient spikes that'll constantly shut you down with the 30 series or higher AMD cards.
That'll get you plenty of eye-candy, no matter what game at 1080p.
Fps will be upto the cpu, naturally a 5700x would be best, but a 5600/5600x would be almost as good, depending on price. I'd not go higher than that as you'll be stepping from a 65w cpu (upto 88w) to a 105w cpu (upto 142w) which will necessitate a higher-end cooler as well as pushing higher wattage than currently used.
If the word 'bottleneck' crosses your mind, at 1080p, throw it out, ignore it. With your pc, there's only 1 bottleneck that will apply. Your psu. It's going to hold you back from doing anything major, requiring you to nickle and dime your way up to decent performance for the money spent.