I don't quite understand what you mean by no "24-bit DR -capable DAC". There are many DACs out there that (at least claim) 24bit or higher. The specs on my Mojo go to 32 bit...
As for ADCs... I'm no expert and can only ask why some sites / studios / ... claim 24~32-bit ADC processing?
For instance, I have a copy of a test recording made by JAPRS and the recording conditions are documented
here. Most notable (to an amateur like me):
"...files were prepared by capturing an identical analog output signal of API console of CR-506 studio of NHK (Nippon Hoso Kyokai: Japan Broadcasting Corporation) with six DAWs, Avid ProTools for PCM 48kHz, 96kHz, 192 kHz and Merging Pyramix/Horus for 384kHz/32bit, DSD 5.6MHz, DSD 11.2MHz simultaneously..."
http://www.avid.com/pro-tools/compare#Pro-Tools-General
Suggests 32-bit 192KHz
and the other goodies listed are beyond my comprehension but FWIW:
http://www.merging.com/products/networked-audio/horus
http://www.merging.com/products/pyramix
But anyway, I have no issue stating this stuff is
way over my head. My only interest is
getting the best possible sound from currently available (and affordable) technology.
If 24-bit (re)production means nothing more than better imaging (if not increasing DR), it's still worth checking out imho...
In terms of
real-world media availability, ok, that's an (even steeper) uphill battle. For example I purchased Davis'
Kind of Blue in 24b-96KHz format without even having any background of where it was sourced
(assumption being of course the original analog masters) or the equipment / studio used to convert it. They sound better than my own CD rips
(to uncompressed WAV files) but that's no proof of hi-res' authority because maybe my CD was made with a low-quality ADC etc. I think the above JAPRS "exercise" is as close as anyone will get to a fair comparison.