Hey Parsons, tbh I think Soul Supremes and Druids should pair well with the same amps as they use the same drivers - Defs are a bit different as they are tougher to drive. I have heard a zillion amps with Zu, so this is my experience.
For SS:
FirstWatt F7 - I've had the SIT-1 and SIT-2 in my system, but just heard the F7 and thought it was great at the LA Audio Show. I think the rumors are this is the best FW amp now
Valvet class A monos
McIntosh - all of them are good, though the quad balanced amps are best
DarTZeel - a lot of scratch though
For Tube:
Quad ii Classics (which would probably be my choice)
845-based amps such as Audion, Sophia Electric, etc.
Mastersound SEP EL34 integrated
I am not a 300B fan, so can't help in that direction. With Zu, I tended to prefer P/P over SET but that's personal preference. I generally don't like SET bass.
For SS:
FirstWatt F7 - I've had the SIT-1 and SIT-2 in my system, but just heard the F7 and thought it was great at the LA Audio Show. I think the rumors are this is the best FW amp now
Valvet class A monos
McIntosh - all of them are good, though the quad balanced amps are best
DarTZeel - a lot of scratch though
For Tube:
Quad ii Classics (which would probably be my choice)
845-based amps such as Audion, Sophia Electric, etc.
Mastersound SEP EL34 integrated
I am not a 300B fan, so can't help in that direction. With Zu, I tended to prefer P/P over SET but that's personal preference. I generally don't like SET bass.