Is this possible? I'm trying to find out if I need to buy a receiver with Airplay or not. Basically what I need to know is.. If I have an Apple TV 4 connected to a receiver with HDMI, can I airplay music to it without needing the TV to be on? Also, if it doesn't work over HDMI, could I plug in a 3rd generation ATV over optical audio and listen to music with the TV off that way? Thanks.