Yep, I use Symfonium too, and it does exactly what I need, but only on Android! I'm looking for something to drive the music at home too, which means I need either a windows client, or a linux client with a web enabled GUI.
I tried Musicbee, but I couldn't get the subsonic plugin to show the music in the Musicbee library. It exposed the music files, but none of the metadata I used to build my playlists from. If I could get Musicbee pulling ratings and last played information over the subsonic API, it would be perfect!
I was hoping there was something else out there at the moment, but if there isn't, it's really good news that it's coming to Navidrome. I'll be patient :)