I don’t claim to know all old DAC’s or oversampling/upsmapling variations. :)
I have been putting DAC’s into the bucket of great bargains AND good
sounding at all resolutions because I don’t remember any DAC having this
combination of consistent performance and low cost in the year 2000.
Very broadly, my impression with "older" DAC’s is you could hear an important difference between low and high resolution works, and there were a lot of different techniques to try to improve the result.
The new breed of DAC doesn’t seem to need these up/over sampling methods but have closed the gap between low and high resolution. :) I’ll give you an example. My Theta Casanova (the little one) did 96/24 great!! Spanked a lot of modern DAC’s at high resolution, but 44/16 was less competitive.
Moving forward in time, my Mytek spanks the Theta Casanova at all resolutions, but ESPECIALLY at 44/16.
These new DAC’s are also VERY VERY good for the money. Fiio is an example of a ridiculously good line of DACs for the money (though amp/headphone matching matters a lot). The UFO DAC sold for a time by Blue Coast Recoreds (among others) was a fantastic USB DAC with DSD capabilities. Mine died at about 2 months from over heating, but (if it had lasted) would have been a great bargain.
Your mileage will always vary. There are some great older DAC’s and crappy new ones. :)
Also, I don’t have the luxury of hanging around stereo stores and harassing dealers or manufacturer’s reps all day. :) So my experience was by no means comprehensive, or constant. I dip in and out of stereo stores as time and money allows. I share these opinions not to try to force others to agree with me but to share my experience, in the hopes others will add to it and create a fuller understanding we can all share from.