What makes a speaker sound great at low volume?


Most of the time I hear music at a low volume (wifey, apartment, ....). 

I am looking to upgrade my current speakers, but in my market scanning I would like to understand, if there are certain “metrics” to look for, before I start going to stores for listening. 

Any advice? 
mtraesbo
"What makes a speaker sound great at low volume?"

The "Loudness" switch on my McIntosh C22 preamp...
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I use the tone controls on my McIntosh C2500 preamp at low volumes.  Does wonders.
I am thinking of getting the Luxman 509x for my office and one of the big reasons for it is the Loudness switch. It would help big time when I am working in my office at 3AM.