It depends, what OS is your phone using. You might experience stuttering (particularly with Bluetooth playback) with PowerAmp if you are running Android 5.0.0 or higher (I did on both my S5 on 4.4.4 and 5.0.0 and my Note Edge with 5.0.1). I had all of my mp3 (mostly 320kbps) and mpeg-4 AAC files (all were 256kbps VBR) on my 128GB microSD card and PowerAmp didn't quite cut it when it came to Bluetooth audio, that's probably because it started using an ungodly amount of resources.
There's also the standard Google Music app, it works with songs stored on your SD card just fine.