Hello, fellow M7 owner here -- I use Poweramp on my device. Note that I have purchased the license from the web store and do not use the Google Play version, that one won't work on the M7. The M7 has a Bluetooth radio. I set my smartphone to Bluetooth tethering and connected my M7 to it so I could share the connection for authenticating Poweramp. It's not a particularly fast connection but it's good enough for doing a quick license check.   I hope that helps!