“Black background” — What really contributes to this phenomenon?

Bob - yes :-) 

One firm noted for early power supply work is NAIM

I like the question. I purchased components already known for their quiet background. I really like a black background and low noise floor, silent computer, etc. And after getting a black background you just found out that your new noise floor is your tinnitus...

Spending more of ones' time listening for flaws...mho...

..but a pair of the DS3's and a good sub would be fun for a change. *S*  Again, mho...

Being single helps immeasurably to all but eliminate background noise.