Dave,

For some reason the centre of your message appears as blank white space on
my screen, but enough remains legible to get your points, I think. I don't
know the full tech details of the installation but I do know that the
speakers are part of a home cinema setup: three front, two side, two rear,
and a separate subwoofer. The amp is a fairly high-end domestic Marantz.
Not sure about the speakers.