I was trying to read through your system list and figure out what you are
using as a preamp for music, is it the ARCAM processor? I'm not in any
way dissing ARCAM, or theatre processors in general (well, maybe a little
bit on the latter), but if you wanted to try see what effect some tubes would
have in your system, a tube preamp or line stage might be the ticket. I
never tried to integrate my home theatre and music systems, so i'm not
sure what that would entail.
I also found that multichannel audio can be very good for some material,
less so for other music. So, I'm not voting against having multiple channels
in your music system. However, you might have some fun trying your set
up (it looks like you could do this as an experiment), by just hooking up a
simpler two channel system, temporarily, and using a really good line
stage? (This may go against the grain of running digital sources 'directly'
into the amps, but if I am reading your system correctly, you aren't doing
that anyway, you are running your sources through the processor?)