D400 VS D-Premier Mono

[Redwingnine]

I have two systems.  One system has a pair of Dynaudio Focus 360 speakers driven by a D400.  I had thought about changing the 400 to a 220, but the advice received was that while a 440 would be a step up, going from a 400 to a single 220 with the Dynaudio speakers would not provide the desired level of improvement.  

I'm using the D-Premier with the T+A speakers.  I'm getting a second D-Premier to run them in mono to drive the T+A speakers.  

While the D-Premier was the initial product released, was under the impression that it's basically the same base hardware design as the Expert series.  Firmware 10.1.0 supports all Expert models, including the D-Premier.  I have compared a single D-Premier to a single D200, and the D-Premier sounds better.  

Both my D-Premiers were just serviced by Devialet, and have 4 1/2 years left on the warranty.  At some point, would like to upgrade at least one of the D-Premiers.  Since a single D-Premier sounds better than a single 200, was wondering who has heard both a D400 and D-Premier setup in mono, and if the D-Premier in mon also sounds better than the D400.