Most of the vintage high end dacs used Multibit dac chips, today these are very expensive and hard to get, some dac manufacturers are even making discrete version Mulitbit for their costly dacs.This gets exactly to the core the issue. I take your comments to suggest that >>>SONICS<<< have not really improved, at least not against the $5000+ DAC's of the 90's. In features and connectivity the old stuff is clearly primitive, but this isn't about that. As it happens I'm running the once-legendary combo of Sonic Frontiers SFD-2 MKIII + Assemblage D2D-1. [see system here https://systems.audiogon.com/systems/6097]
If you want just to get the best from your 15,000 PCM Redbook cd’s then go either new age Multibit, which will cost you, or >>go used vintage hi-end.<<
One vintage Multibit cdp I can particularly point you to, would be the Mark Levinson ML39. good luck finding one, as they need to be pried away from their owners.
By my reading the SFD-2 MKIII starts where the ML39 leaves off: PMD-200 filter (upgraded PDM-100 with HDCD and more) vs PDM-100 in ML39 and 8x PCM1704 D/A's vs 4 in ML39. SF said at the time: "These chips are placed in a fully balanced topology with 2 converters in parallel per channel per phase." It's fully balanced throughout (of course ;-) and goes up to 24b/96khz with lots of other technical bells and whistles that I don't understand.
So, if the ML39 qualifies as superb vintage high end kit then the SFD-2 MKIII certainly would too - though it's even more obscure and was produced in tiny numbers. All the tech stuff wouldn't matter if it didn't sound good - which it does! Superb in fact. It has no sonic shortcomings that trouble me, my concern was that advances had left it behind. I'm not interested in all the hassles of researching, auditioning, shipping, yada yada if the odds aren't good that I'll find a major audible improvement for less than $3000 (kind of arbitrary budget).
Elaboration or rebuttals welcome. Cheers!