Side note, the original AD-122 seems kind of lost to the sands of time, I can't even find any specs beyond its 122 dB (unwtd) dynamic range. I did find out that they (and the MkII) like to run hot, as things on the bleeding edge often do, and that early units generally cannot be serviced due to parts unavailability.
I've come across a 32-bit ADC with a 90 dB dynamic range spec in some modern-day headset codec thingy, thought that was kind of hilarious (50% of bits being pure noise).
By 1990, the best mainstream IC converters were good enough to warrant more than 16-bit (which meant 18-bit) output, and by 1993 the first 20-bit jobs popped up. 20 bits was found in converters like the Focusrite Blue series by 1994 and became all the rage in prosumer soundcards in 1996, and then the next year the first 24-bit jobs popped up (of which even the best ones barely needed more than 20, but I guess people found handling 22 bits awkward and the data stream already supported 24 anyway).
The '90s were a wild time. Imagine going from barely 100 to almost 120 dB of dynamic range in like 7 years. By the end of the decade, performance approaching custom, hot-headed cost-no-object designs like the AD-122 became available in volume production (still expensive but no longer involving a kidney or first-born). By 2004, any reasonably well-heeled enthusiast could buy an EMU 1212M for like 200€.
(Mind you, in the same time a new PC probably went from a 386 with 1-4 MiB of FPM DRAM to a 233 MHz Pentium II with 64-128 MiB of PC66 SDRAM, and then a 2.8 GHz P4 or equivalent Athlon64 with 512 MiB to 1 GiB of DDR/DDR2 SDRAM. That's "a bit of a difference", too.)