I suggest you definitively confirm with Xfinity that the audio is indeed being broadcast in 5.1 with audio coming from all channels. As others have noted, I have heard that many on-demand programming is only in stereo regardless of what the signal is to the processor. So before driving yourself nuts, confirm that to be the case. The fact that you are getting 5.1 from other channels almost confirms this. I highly doubt the issue is with the Anthem and it's not a bandwidth issue with toslink or S/PDIF. You can get 5.1 just fine through those. Bandwidth limitation over those is only normally confined to lossless codecs.
