What should I replace

[ExileHarmonicYT]

I recently changed my cpu from i5-2500 to i5-3470 and my gpu from rx480 to rx580 but the games I want to play (fortntie, apex, cold war, fivem, modern warfare) will perform under 25FPS. The only game I have that performs higher than 50FPS is Rust and Rocket League. Ive factory reseted my pc, updated drivers but still nothing. The games even struggle to run at low settings. What should I do?

 

old specs:

Dell OptiPlex 7010

i5-2500

16GB Ram

RX480

120GB SSD

3TB HDD

500W APEVIA PSU

 

new specs:

Dell OptiPlex 7010

i5-3470

16GB Ram

RX580

120GB SSD

3TB HDD

600W APEVIA PSU

[Toolace]

Unless you're not getting enough airflow throughout the case and aren't thermal throttling, I'd have to guess that maybe the motherboard isn't handling everything too well. If the motherboard is not the problem, then maybe the CPU? The CPU seems to be the most dated part in your build (although I havent seen the motherboard). 

 

https://www.gpucheck.com/game-gpu/fortnite-battle-royale/amd-radeon-rx-580/intel-core-i5-3470-3-20ghz/

 

Although PC benchmark isn't entirely accurate to say the least, your CPU and GPU combo is expected to get far better performance than what you suggested (unless you're trying to run 4k epic settings or something). But ya, I'd try to check bios for any abnormalities, then maybe get a new motherboard/case if all else fails so you can keep your other main components. Good luck, cheers!