Some tidbits for those of you trying to get your Shield working with high-end audio:
Plex and Kodi don't yet do proper passthrough of full DTS-HD MA with 7.1. Plex is currently working with Google to finish support.
ES File Explorer can play it with the built-in Shield media player, which Nvidia hacked proper support into. I haven't been able to scrub MKVs with this, however.
Thanks
Also another FYI, following that, I've just tried some other files in the built in player and can confirm that Dolby Atmos passes through okay too.. Which is contrary to what I've been told previously, even by nvidia!