In addition to Otto’s suggestion to output the music from Plexamp on your phone to the Van’s audio…
There’s already existing suggestions for Plex to support exporting media / playlists to an external medium (those talk about USB sticks / thumb drives; burning discs seems to predate that).
- Export Music Playlists directly without need for external custom apps
- Export music playlist to m3u+media
If you truly can’t go with the option suggested by Otto, you might want to comment/vote in (one of) those threads to help us avoid distracting or cannibalizing votes.