So I installed this card from an R9 290 and I am not getting nearly the performance boost I expected. In Assassins Creed Unity, Deus Ex MD, Dishonored 2, and DOOM I'm getting 60fps at 1080 rarely consistently. More like low 50s high 40s. even drops into the high 30s. Something just does not seem right. I ran a PC benchmark and here are the results
You using Windows 10 1903, the most up to date drivers, and did you use Display Driver Uninstaller to do a clean install when you installed your RX 580, which, by the way, is only marginally faster than the R2 290 (about 15%)?
According to that benchmark it is your SSD and CPU which are the problem areas. Run Cinebench R15 (not R20, your CPU is too slow for that), and see if you score around what Bit-Tech got, 594, or CPU-Monkey, 534.