Hi John,
The answer to your question depends on several variables. Just because you have plugin capabilities for more speakers than you presently use doesn't mean (necessarrily) that you should use them unless they add to a certain auditory experience.
I have an upgraded Denon 5800 which makes it about 95% a 5803 and I use 9 speakers but not necessarily at the same time.
I've jumped into both DVD-A and SACD with both feet. I have over 300 discs, some of which are srtictly 2ch.
It was important to me to have a matched set of audiophile grade speakers for music so I purchased 5 Totem Model 1, with Signatures as the front 3 and bi-wireable but non signatures as my L/R surrounds. Except for the Sub all other speakers are off when listening to music.
For film, I add on (more towards the center of the room) a pair of Axiom QS4 Dipoles (surround B) and for the EX or ES effects that some films now offer I have a pair of Monitor Audio Bronze.
None of these extra surround speakers would operate as a separate channel unless it was a DTS ES discrete sound that had been created by the DTS sound engineer. I think Dolby Digital only creates a martixed or mixed channel for their effects channel.
All of this to say is that if I had all the speakers on including the Subwooffer for a standard 2channel show or cd, the face of my Denon would show 7channel stereo. So depending on the size of your room and the type of listening that you do, you've got lots of options but unless adding speakers adds something to the experience for you, there's no law that says you have to add speakers.
Peter m.
