How is the Pass Labs X150.5 at low volume?

Just speculation as I've never tried it but the Pass with a good solid state pre or less tubey pre maybe could do it for you. A Florida Pass dealer I know suggests VTL pre with Pass amps. They can be had used at pretty good prices. He pairs those with Wilson speakers if that helps at all.

Somewhat similar to @audiojan I have a Evo400 pre that I tried with a Pass 150.8 and didn't really like it. I would not use it for low level listening to say the least.  My typical volume maxes out at 80 db peaks and it sounded slow, unemotional and non-dynamic. Maybe it needed higher volume levels to bring out the best but I don't listen that way. Ayre amps have a very black background that I find works perfectly for lower levels.  It's hard to explain but it's different from anything I've heard. I use an older Ayre V-5xe with the Evo400 and am currently listening at about 53.3 db (just tested using white noise and not very accurate iPhone NIOSH app) and miss very little of the music.