I've a pair of Apogee Duettas that have begun the dreaded "buzz"
B&W DM600's down from their perches
'90's Adcom GFA555II driving them
To be honest, every time I've listened to Duetta's in the past, the sound has always been lacking. I get the feeling it's extremely difficult to set them up correctly in the room and to pair them with synergistic equipment. Or..most may have a range of aging and wear not meeting factory spec.
On the other hand, every time I've listened to B&W DM600's through various series, they've always sounded at least fun and involving, if not dead neutral or refined. I get the feeling it's much easier to set them up.
The Adcom 555 II.. I can see how it may be synergistic with the B&W, but if I were looking for reasonable amps of that vintage, I would look towards a good used Aragon, Adcom 5800 (Nelson Pass designed), Marsh, etc.