Thanks mahughes and hilde45 for your posts. Re the node 2i, yes I'm considering that. I keep hearing that the bluesound stuff is "entry level high fi," but if the DAC is what's important and I use a it just to stream, and if the the power supply for the streamer is next most important, which I think is also true, then your solution makes a lot of sense.
mahughes, thanks for the question. The "sound" I've always looked for is something like this: 1) tonality of vocal music. On the very best systems I've heard, Leonard Cohen on "You Want it Darker" sounds not only deep and gravely but actually old. Beverly Glenn-Copeland on "Deep River" sound like trans, with that beautiful fold contralto he had as a woman overlaid with the masculine tones he acquired after transition. I suspect this has a lot to do with handling different dynamic levels, because tonality is largely a function of harmonics, and the harmonics of a note are much quieter than the note itself. 2) separation and distinction. When I'm listening to Trombone Shorty or Roy Hargrove, I want to clearly hear the differences in tone between the saxes, trumpets, and trombones. In good choral recordings on great systems, you can hear the distinction between individual voices, both the unity of the chorus and the individuals. 3) coping with complexity. On pieces like the Dance Infernal in Firebird or John Zorn's noisier stuff, or maybe Frank Zappa, you often hear a kind of confused failure-to-keep-up that's clearly an artifact of the equipment (though I think more an amplifier or speaker problem). Slam/attack and decay. A rimshot should startle you; the opening to Born in the USA should jerk you upright a little bit.
Anyway, that's the best I can do at describing the elements that add up to what I'm really after, which is being transported by the music.