Here is a curated list of the most requested presets on forums. Search these names in the sources above.
This gives you a "scientifically perfect" flat preset in under 3 minutes.
Reviewers and users generally agree that Poweramp's EQ system is "unmatched". It's praised for being yet deep enough for professional use, though some find the "endless fiddling" a bit engrossing. The main complaint often stems from DVC (Direct Volume Control) instability on some devices, which can sometimes affect how presets sound.