I am using Plex with the Alexa app for voice control. When I ask to play a movie or TV show it works fine, with the audio output through my AV receiver. But when I ask to play music, the sound is output through my echo rather than my audio receiver. I have been unable to find how to change this behavior.
I have the same problem I posted about here; http://forums.plex.tv/discussion/317851/alexa-sees-player-but-doesn-t-send-commands
So +1 to this thread.