Need help to select a speaker

Nothing good about Dynaudio at low volumes. Good sound at low volumes is complex and not related to sensitivity either. There are some speakers with a deserved reputation for good sound at low volumes, Harbeth comes to mind.

How your system attenuates volume matters hugely in this equation too. Autoformer volume controls like those from Slagle excel at low volume listening as they are at max current when at high attenuation, unlike resistor ladders.

As a rule 90% of the low sensitivity monitors out there with main drivers in the classic 6.5" range sound best with SS amps that thump a bit in the midbass (ie Pass) That is where many fall short at low volumes, they need to be playing louder to come on song and sound balanced. An amp that hits a bit harder can make up for that at lower volumes.

Old Tannoy professional system 10 and System 1000 are excellent at low volumes and don't need a ton of power to be on song at low volume. Pretty sensitive too.

ATC‘s don‘t compress and are fine at low vols

Hum funny my temptations are fantastic at low volume. 

@inteliaudio -

For smoothness and low distortion, it's hard to beat electrostatics. You might consider the Janszen Carmelita passive. Janszen's current lineup are unusual (if not unique) among electrostatic speakers in not being dipoles.

As you might expect, the speakers are somewhat directional in the high frequencies. This leads to a somewhat smaller sweet spot (though not head-in-a-vice), and also means greatly reduced interaction with the room, so less trouble with reflections from sidewalls and ceiling. Bass is handled by cone woofers.

I use the bigger model, the Valentina passive, with Apollon amps built around the PuriFi modules -- if I'm not mistaken, the same technology used in your NAD M33. I find the combination to be excellent, the best I've had in my many years of owning audio systems.

I love my ATC SCM 11 v2s, which I use with an REL T7x sub. With your budget, you could step up to the 19’s, which would likely be better yet. I listed to classical, alt/indy rock, acoustic music with vocals, and heavier rock, and everything sounds great, including at 65-70 db, which is where I do most of my listening.