I have a Sherbourn (currently up for sale) and it has what they called "side axis" speakers. The channel was derived from FRONT RIGHT W/SURROUND RIGHT and FRONT LEFT W/LEFT SURROUND
It created an extremely wide front soundfield that was very impressive - especially with a film's music. In this setting music has a more open and richer frontal soundstage. Instead of being simply FRONT LEFT, CENTER and RIGHT it had spread more akin to an ochestra laid out in front of the viewer.
I don't know if this feature is the same for all companies but that's how it was on the Sherbourn.
I have M80s and a VP150 center so I chose to use a pair of M2s for the "side axis" channel and the sound was seemless.
