SirQ:

You are probably correct; however, I'm confused after reading your post again.

Am I wrong in thinking that when Audyssey tells my Denon AVR that the -3 Db point is ~40 Hz, it sets the Xover there but also sets them to 'small'? Why is Denon's suggested setting of 40 Hz for supposedly 'small' speakers?

The prevailing wisdom is to then manually set them higher (but never lower). I can see the reasoning for this - to let the subs take on more of the load in the <80 Hz region where they often work better than most mains.

Despite a lot of reading on this subject, I guess that I still don't really have a grasp of this tool...

TAM