Not sure if your Denon works the same as my 2807 but you don’t have to use Audyssey. You run the auto setup and then just turn Audyssey off. Personally I find it’s faster just to grab a tape measurer.
You can just go into the Denons setup menu and tell it if you have rear speakers. It should allow you to select between none, one or two.
Dolby PLIIx will only pull out matrixed information if it’s recorded that way. It will also pull out ambient sounds even in non matrixed 2.0 and feed it to the side and rear speakers. How well this works depends on how much ambient sound is present on the recording.
