Regarding specs - here's answer from the Apogee Tech support:
"With regards to specs, it is important to keep in mind that specs do not tell the whole story. A good example of this is the Rosetta 800, which on paper does not spec out as good as the PSX-100 or the AD-8000, yet sounds a great deal better than both.
It is important to keep in mind that component manufacturers are in the business to sell their products just like we are, and knowing that most people hear with their eyes as much as their ears, strive to reach higher and higher specifications on paper to attract buyers. What we have found is that this does not always translate to better sound quality.
Each time Apogee designs a new product we literally listen to each component and series of components to determine what is the best combination for that box. If the spec is not as good on paper but the box sounds better, we will go with the sound every time. For the Rosetta 800, we could have chosen components with higher specifications; instead we chose the best sounding components.
All that being said, Duet’s (like Ensemble’s) dynamic range is 114 db and THD+N is -100 for both A/D and D/A. While that is very close to the Rosetta spec, the Rosetta’s analog section and power supply are both superior to Duet (as well as Ensemble), giving the Rosetta the edge."
So here's the answer. And as most of the DUET users here will confirm, DUET does sound good!