My situation is similar to yours. I suspect source signals.
My HD which is OTA changes by channel and program. Some have no center, some too much bass. The Denon shows 5.1 for true HD channels and stereo for SD digital.
My basic cable (no box) shows no signal type on the Denon, but is processed to 5.1 by the Denon.
Both basic and OTA come from the same digital out on the SXRD.
For the programs with no center, the mains were phantoming or I change to PL music to change the soundstage. Too much bass means changing the sub volume. (I wish Axiom had a sub volume remote.)
