Pass, Bryston or Accuphase for Magnepans?

”I tried the Bryston 4B3 with my 3.7i's. It was not particularly good.”
What was it you didn’t like about the Bryston?
A friend of mine tried both the Diablo 300 and Progression int and preferred the Dag.

Why not ask the speaker manufacturer? I bet they demo them with certain amplifiers when they are designed and voiced. 
 

Currently using the Pass 250.8 with 3.7i it has a great sound and plenty of power, slam and dynamics. I think this combo won TAS best at show a few years ago.
I did plenty of research and didn't find anything but positive for the Pass and Maggie combo.

"What was it you didn’t like about the Bryston?
A friend of mine tried both the Diablo 300 and Progression int and preferred the Dag."

Swede58, while it has been some time since I made the comparison of the Bryston 4B3 and Gryphon Diablo 120, the Gryphon was much more realistic sounding.  The soundstage was wider and deeper.  The Bryston was just less involving and boring to listen to.  I will say that had I not had the Gryphon to compare it to, I would have thought that the Bryston was good, but not great as the Gryphon was.  As to the Dag being preferable over the Diablo 300, I cannot comment from personal experience as I have not heard the DAG.  But, I would guess it to be excellent by reputation.  I also have heard some say that the Diablo 120 better the 300 depending on the system.