From Bell Canto REF600M specification/features page:
"The Bel Canto Impedance Optimized Input Stage is a balanced high Common Mode Rejection, low output impedance driver that is critical to the amplifier's performance, ensuring that the refined dynamic qualities of the recording are preserved."
This is what will give this amplifier its "bell canto flavor", and separate its performance from the rest of the Hypex based designs.
BTW I listened to a system using the NAD M22 two weeks ago, and wasn't impressed. The comparison was against an Accuphase integrated costing twice the M22, but not a lot more than M12 + M22 combined.
Is it just my experience, or Hypex (in general) requires very, very careful matching upstream? (downstream they are as speaker independent as I ever heard).
I would love to hear other users experiences.
