I've got myself one of those new Chromecasts with GoogleTV (which in itself runs on AndroidTV and has all it's apps). Video streaming services all work nicely so far. And with some effort, I could install Kodi with the Subsonic plug-in to play my Astiga library, and with the Kobi last.fm plug-in I also got it to scrobble. I'm also rather happy that it can use my playlists etc from Astiga in Kobi.
However it's really clumsy in usage when you want to browse songs. The Kodi Subsonic plug-in isn't very user friendly for those with big libraries. You need to scroll trough the entire library to find stuff and it takes a long time to load larger folders. Next to that I need to start up Kodi just to start-up Subsonic to access my Astiga files instead of moving into my music library right away. It also doesn't support anything above 320kbps (it compresses higher files). It also often can't load album art to the ambient screen, resulting in a Kobi logo standing there most of the time. Yet, despite all those downsides, I couldn't find another Subsonic app that works on Android TV either.
A Native Astiga app would be a really nice alternative, since the current Android app can't be installed under normal conditions and Kodi is maybe a bit much when you just want a simple music player.
Perhaps the phone app can somewhat easily be made compatible with Android TV using the tablet-friendly interface (which I'm assuming exists since I have no tablet)? Or else something based on the web interface (which I guess would be easy to handle with the arrow buttons on most remotes including the Google one since they have clear "boxes")?