Although my AVR is PCM capable, I have noticed that with all the HD boxes from DISH that I have had, PCM is a fleeting thing. It only works with Optical Out, or you get nothing, or you lose Surround Sound and only get stereo from the AVR. I've played with that before posting here and have also found that it depends on the product you are viewing and what they are sending it as and what DISH is passing on. It varies.
ALSO, lately I have really noticed that the volume from channel to channel can be deadly. And this is a DISH and network issue. There instances where it's just the networks and DISH does not accommodate the difference. Like having Aljazzera tune in and watching a recorded program and when it's over or you go to the DVR and the AJ audio hits, it HITS. But then there's the ones like Comedy Central, where they have some on their programming in Stereo and when it goes to a SS commercial you get blown out. So with all this it makes the CALM Act a moot point. Plus I have noticed that commercials are louder now. So not only is a moot point, but a null one.