You're not going to like this. The specs for audio read:

Support Music Format: MP3/WMA/AAC/WAV/OGG/AC3/DDP/TRUEHD/HD/FLAC/APE

In there you see AC3. AC3 is Dolby Digital. But Amazon and Netflix stream in EAC3. EAC3 is Dolby Digital+.

Since the box doesn't support EAC3, it can only output stereo rather than multi-channel.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated