For my 2 main listening devices (car stereo and Jabra Bluetooth earbuds) the best setting I can get with any music player I've tried including Poweramp, is by using a specific convolver that I have found.
I have tried for quite a few hours to get the EQ in Poweramp adjusted to sound the same or better than the setup that I use with the convolver and I just can't get it. I wish I knew of a way to inspect the convolver and see if I could translate it into EQ settings but I'm pretty ignorant on the technological differences between EQs and convolvers so not sure if it's even possible.
As awesome as Viper is for being a system wide EQ and stuff, rooting phones is getting more and more difficult to find with the specifics of what I want in a phone and also the fact that it is closed source and not in active development anymore.