What kind for interconnects and what digital cable? The AMC is the transport?
I also wonder if your HT preamp is a weak link for 2 channel audio?? Are you sure you are not re-processing the digital sound through the HT decoder a second time?
I also wonder if your HT preamp is a weak link for 2 channel audio?? Are you sure you are not re-processing the digital sound through the HT decoder a second time?