Edit: Fofer pointed me to this thread after I posted a new topic, and I accidentally posted the response here. I will also post the response in my thread.
Thanks! I did try BackgroundMusic but it did not work for me. After looking at their troubleshooting section, I found this:
"Only 2-channel (stereo) audio devices are currently supported for output."
I got horrible distorted audio through my AVR. However, it did seem to work fine with my Mini Mac's internal speaker. So I do not think BackgroundMusic is an option for a multi-channel AVR. The SoundSource app did work fine in trial mode, but that only lasts 20 minutes or to and then they start pumping in white noise.
I will test the other two. Right now, I just use Safari to pull up the Channels Server webpage on the Windows PC running Channels Server, and I can playback in a windows and use Safari to mute the audio, but I prefer the iPad Channels app. Also, I do not get anything from the rear speakers using Safari.
Does the iPad Channels app running a Mac even support 5.1 channel sound? I have not tested this yet, but I will.