Seems to be that D/A converter for audio has reached its peak...
If you are pursing better sound quality, I think your focus should now be on speaker and amp, assuming you have a very good DAC.
It's become quite apparent that speakers are the weakest link in the audio chain. Very decent electronics can be had for a small fraction of what very decent speakers cost, and even then those speakers are still going to be the weakest link.
Steven Stone of The Absolute Sound wrote... "Within their product categories the DAC-10H DAC/preamp and ST-10 basic power amplifier are priced at the lower mid-level,
yet they both deliver performance that could be considered exemplary regardless of cost. Unfortunately, that can't be said about anyone's speakers.
However if Nuprime made speakers offering as much
performance and value as their electronics, they'd own the speaker market.

Upgrading DAC-9 or DAC-10 has diminishing return.
You've always been very candid about that, but there are other features that made the DAC-10 more compelling choice for me. And even though it does cost more than the DAC-9, it still a fraction of what some people charge for their DACs.