goldwing, I can’t see what is going to my AV system as it is a soundbar system, and even though it is a high end one, it doesn’t have the bells and whistles an AVR might have. All my testing is with my ears. On the FireTV in order to get 5.1 you have to set audio to Dolby Digital only, Best Available seems to always be DD+. DD+ would be fine if all the source material is at least 5.1, but much of it from live streaming isn’t. So far it seems to me the only live channel streaming service that has anything but stereo is ATT TV and Now, and that only on some channels. Notably the premium movie channels. I do remember that AMC is also in 5.1. I don’t use the FireTV much at all because the AppleTV I have is just so much better. But if I have time today, I’ll fiddle with it and report back.