BEST SPEAKER THAT COMES TO LIFE AT LOW LISTENING LEVELS

My Fleetwood Deville SQ sound amazing at lower volume.Mids and voices sound awesome especially now that I added 2 Rel S510 subs. I too cannot listen at too high levels as I have some degree of tinnitus but my setup is perfect for listening at low levels without any details and dynamics lost.

Fischer & Fischer SN 370's. The slate cabinets cannot be beat for what you're looking for. And they are $15k/pr.

I’m not sure you can do better for low volume listening, as electrostatic speakers are known for their resolution at low levels (mainly due to the lack of mechanical hysteresis - getting that heavy cone up and running - in dynamic drivers) and your Martin-Logan’s are definitely fantastic electrostatic speakers.  Panel speakers, like yours, are very nearly line sources whose sound pressure decreases 3dB with each doubling of distance (the inverse law 1/r) where as point sources (cones, domes, etc) follow the inverse square law 1/r*2 where sound pressure falls off by 6dB per doubling the distance.  I think maybe some EQ options that others have mentioned might be the best solution. A Schiit Loki+ 4 band EQ at $149.00 between your preamp and power amp would handily do the trick.  It’s totally transparent, easily bypassed, and made in the USA.  The Lokius at $299 takes you to 6 bands and balanced in/outs. The Loki Max at $1499 adds remote control to all the controls. Enjoy your great system!

JBL 4349.

You have a very nice rig.
I’d start with a Schiit EQ. You can use it like a variable loudness control. The top of the line even has remote.