Magnepan 20.7's & Tube Amp

Depends on the size of the room, type of music, and how loud you listen to your music. That said, the closest experience I have is driving 3.7 model with Cary SLM-100 @ 100wpc, in an average size room and I felt the speakers were starving for current at medium to high volumes. 

Ralph, is the need for the very short speaker cable unique to the planar/OTL combination or long cable inherently causes low frequency roll-off? I didn't think the cable length should be that detrimental given a 1.75 ohm output impedance on the MA-2.

The original discussion was about 20.7 and not 3.7. And in general, I tend to put more weight on inputs from practitioners than from the manufacturer. To each his own.

Congratulations. Your 8’ cables, especially of such high quality should not pose an issue but a pair of ARC 250SEs as compared with an ARC Ref110 may give you different results. I’m sure I’m stating the obvious but you may want to try the larger Magnepans with your amp if the dealer is local. Nothing to lose and just gain a peace of mind.