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

Now this is a timely post. Last Friday I went on a tour of the ARC facitlity
in Minneapolis hosted by the gentlemanly Dave Gordon. If you see a
Bat logo on a reserved parking spot and a car is parked in it you will
know if the Commissioner is in or not. 

FYI Friday is a good day to request for a tour as they are mostly all
on 4 day 10hr work week. ARC was taken private 3 years back
and for this reason I was motivated to learn more as comglomerates
tend to lose product value in my experience.

The facility is spotless and very well organized. The repair room-manned by two techs- was model of organization and that alone surprised me.
We were shown their new I-50 Integrated which ships next month.
I predict ARC will be on a fast track to even greater success soon.

I only listen at levels of 55db to 69db. So low level performance means
a lot to me. When you ask most manufacturers what factors in a speaker
or amp's build improve low level sound I seldom hear a straight forward reply.

Currently I use a Pass INT25 with Tannoys rated at 94 Sensitivity at 4 ohms. I think it does a very good job at low levels. Prior to that I used
a Cary 120 Tube Amp which provided excellent musicality but did present all the detail the Pass does. Nelson Pass believes his Amps are more "Tubey" than other SS amps. Now after seeing the new ARC 50 INT I am sorely tempted to try tubes again. Auto-Biasing and a built in clock will simplify maintenance. The Pass gear is bullet proof and musical. Both are pricey.

Does anyone have experience comparing the low level performance of 
Solid State vs Tubes?

No experience with X150.5, but low level listening with XA60.5’s we’re quite good.

on a related note… I tried PrimaLuna Evo400 pre with the XA60.5’s and it just didn’t work well… poor synergy

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. 

@ghdprentice Superlative set up man! 🤯
I appreciate all  the responses, to be clear this is basically just a matter of opportunity. I really love the D400MKII. If I had the room, I’d grab the Pass and keep the ARC. I highly doubt the Pass would disappoint me at any level but at the same time I don’t think it would be a jaw dropping upgrade, which is why I’m hesitant. My intentions have been to upgrade the preamp next…but this Pass came alone and grabbed my attention.  🤷🏼‍♂️

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.