I haven't noticed any connection to volume, although I listen at a fairly loud volume consistently. I like the instruments to have a certain weightiness to them, if that makes sense.
And I shouldn't exaggerate the severity of the problem. I notice it most with high pitched instruments: a flute or vibraphones, for example. I can hear a certain exaggerated resonance when the vibraphones get to a particular frequency, though I couldn't identify the frequency for you.
Otherwise it is only obvious with poorly recorded CDs that have a lot of digital glare in their own right. The brightness isn't a problem most of the time, which is why I haven't felt any urgency about replacing any of my gear on that account.
My DAC is a SimAudio Moon 300D. I'm curious to see how much of an improvement the BDA-2 delivers.
My preamp is the first edition of the SimAudio Moon P-5. It dates from c. 1998, if I remember correctly. SimAudio was just creating the "Moon" series at the time, and in fact my P-5 has Celeste on the remote. The faceplate is the old SimAudio logo -- it doesn't say "Moon" anywhere, although the next edition of the P-5 had the Moon logo.
I have two YBA3 power amps set up as monoblocks. Again, quite old -- older than my pre-amp, even -- but I really like the sound of them.