Can Tube Amps be Used for Home Theater?

Actually a hybrid would be much less of a problem for continuous operation . Usually the hybrid is only one 9 pin dual triode miniature tube. I think that they rarely do much in terms of delivering the tube magic but others disagree. These small tubes run at much lower voltages use little energy and last a long while (10,000 hrs some claim). Still all SS maybe your best bet in terms of sound quality which is obviously your goal .

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?)

I have a pair of Class D hybrid monos, from Arion Audio (500w pc) in my stereo-HT system. Believe it or not, they replaced a BAT VK600SE (a formidable amp). I leave them on all the time and the sound is out of this world.

Well i was looking at the Conrad Johnson ET250S. Any one have any experience with this amp?

Look into the Butler Audio TDB (Tube Driver Blue) 5150, 5 channels of 150 wpc with a 6SN7 tube (run very conservatively) driving SS output. I leave mine on all the time - about 6 years now - with no heat issues. Gives a nice blend of tube harmonics and SS bass grunt.