Just my 2cents as the D-1 is way over my "budget"....but from the discussion I smell BS marketing, lost in measurements.
But Misti's question of how can a DAC expand dynamic range above recorded levels reminded me of actually hearing an improvement the other day. Listening with three different stand alone headphone stacks to a standard rebook cd of Dire Straits it was obvious that the top tier stack (OPPO 83, I2s, Pontus II 12th, Holo Bliss KTE, Susvara OGs) on some of the very low volume vocal intervals were more detailed and "hearable" while at the same time sudden drum hit or guitar note were still very fast and textured and suddenly loud, compared to the 2 lower performing systems.
That is what dynamic range we're discussing here is, right? That is, the lowest level sounds at the same time VS the loudest sounds. The faster a DAC can react, the better usually. Beside speed the other how is probably in the DSP processing mentioned in the D-1, raise the low volume, increase the high volume, maintain average volume.
As far as increasing it above the recorded levels that's almost a remaster on the fly and very probably subject to "taste".

