I managed to install Poweramp v3 on mu Asus ZenFone 2 (yaaaaay!) and the app works pretty fine now, though it kept crashing when I first opened it. It stopped crashing and started working as it should only when I changed the list of folders to be scanned.
Polish translation is pretty bad in some places, by the way. I mean, messages like "tu nie ma nic dla mnie" (shown when there's no music files in a folder) look like very un-professional translations. Is it possible to correct them? Maybe you could send Polish translation to someone (maybe to me) to correct them?