When I added my external DAC (Gustard X26 Pro) to my Parasound P6 pre A23+ amp based system I stopped using the pre remote to control the volume as I was intrigued with checking out all of the different settings on the DAC. Based on another discussion here I set the DAC volume at 100% (so that the DAC digital volume circuit isn’t involved) and went back to just using the preamp to adjust volume and SQ improved.
I don’t mean to suggest that the Parasound pre is exceptional (I am in the process of deciding on a tube pre to audition once I replace my amp (probably with a Bryson 4b3), but offer this anecdote as to one benefit of a preamp Inhave recently observed)