I'm having an issue with my HTC One M8 and using it to stream audio over bluetooth. On my last phone (VZW GS4), when I connected it to my Flex's stereo (Sony SYNC with nav), it would list in the bluetooth pairing as connected to phone & media audio. However now on the HTC One, it only shows phone audio.
I have searched all over and couldn't find any info on this issue and there doesn't seem to be a setting in the stock ROM to set it up. The system still works with the phone when using it for phone calls.