Okay, I guess I'll chime in here, as we've spoken over email about this, but maybe this will be helpful for others. I own the MS4's and am happy with them. They can be though, as Tvad said, analytical. I find them extremely sensitive to changes up the line (especially with cables) and am going to spend some time trying to find a nice synergy in my system before I entertain switching to something else. They're not necessarily forgiving speakers, and are going to reveal weaknesses in bad recordings, but they do wonderful things with sound-staging, micro-dynamics and vocals. Low-level listening is very pleasant, although I tend to listen at higher volumes. I think given your amplification, most of the speakers you're entertaining will sound good at low levels, because of the Pass's Class A bias.
Now are they the perfect speaker for you, I don't know. I think you should listen to them, but I think that something else to hear is the Verity Parsifal Encore. I really love what these modestly-sized speakers do, especially at low level. They are nothing close to analytical, but are still resolving and articulate. They're pricier new or used, but I think that's a speaker you could be happy with for a long time. It's also nice that you can position the woofer to fire forward or backward depending on your room's setup. They're also beautiful in the Makore finish, IMO.
Enjoy!