Capq,I had a Krell KPS 25sc some years ago. I was kind of thinking of this, cheap drive units compaired to expensive. So, i connected my $500 Pioneer dvd as a drive unit to the dac of the KPS 25sc. Wow, what a difference. The soundstage was flat, bass was virtually dead compaired to the slammering krell transport. Sound was thinner etc etc, well. I can say, it was a totally different unit without mention all here. In this specific design, it was more than night and day. I have also been trying some drives with the dac 1. It is no obvious difference. I also confirmed this with Benchmark. I am no tech, but i can hear. No use in buying a world-class drive unit for Benchmark. Sadly many seem to fall victims of payning to much for to little and placebo effects is a common disease. Been there, done that:(
If an upgrade would be of interest, maybe the analog part could be modified further. I have a very good moding company over here. But, moding the unit costs as much as the unit holds in second hand value. Not sure it's really worth it at thsi moment, for me. This does not affect the gain of the level control either, just the analog part.