A nice mid-fi low listening levels choice is the new(ish) KLH Kendall. They're about $1,300 USD and certainly certainly not in a class with Harbeth or most of the other things that are being suggested. But they are designed to sound good at low levels. They are respectable at moderate levels and poor at high levels due to distortion - but that's what you get for that price. The key here is that they really seem to be designed for low volume listening, and they are 3-way so the highs and lows get a little more devotion than they do in 2-way models.
I had been looking for speakers that sound good at low levels for many years and was seriously considering Klipshcorn, Belle Klipsch or JBL S4700 because I had heard them at low levels and was really impressed. Of course those all cost a lot more, and those can also play really really loud. Then I ran across the reincarnated KLH and on specs alone decided the Kendall model was worth a gamble. I think they are great at low volumes! Of course they don't do loud very well, because they aren't designed for that. But at low volumes, which is what I am always looking for, they are wonderful! They do not have the flexibility to be house shakers and stay clean sounding, but if low levels are the primary objective, they are a steal in my opinion.
To me a speaker that you don't have to turn up to enjoy is a great speaker. I wish the "reference level" of most home equipment was lower, but of course it's mostly determined by comparison to live performances and that's usually pretty loud.
Incidentally, I think the KLH Kendall is a fabulous budget classical music speaker. It is also great for Techno Dance if you want it to be really really quiet - but who wants to do that?