I have my music collection sitting as FLACs on my Multimedia PC, connected to my stereo System. I also have a service running that mirrors my music collection by converting it to m4a files and automaticly sends it over to my phone once it connects to my home wifi. I have set up the conversion (qaac64) so the difference between a flac and the m4a file is unnoticable over my bluetooth buds (playing the m4a from my phone).

While I cant hear the difference on my phone, I definiley can hear a difference on my stereo / hifi headphones