The discussion raises some interesting points. Some are more easily dismissed (i.e. the role of speaker wire) while others may be more relevant (the mental status of Ian and me, ha!). But one parameter that might be most relevant in sorting things is the issue of amplifier damping factor.
Damping factor is the ratio of the rated impedance of the loudspeaker to the source impedance. In solid state amplifiers, the damping factor usually has a maximum value at low frequencies. A quick read in Wikipedia is informative and provides many fine points and provides comments from such luminaries such as Toole, Atkinson and Pass. The “In Practice” section is particularly relevant. However, the one thing that is missing when considering amplifier performance comparatively is the actual reported damping factor for the JC1+ and M10 (or its relevant cousin, amplifier output impedance).
Unfortunately, I can’t seem to find it for the M10. The damping factor of the JC1+ is specified as >1200 @ 20Hz. Wouldn’t that be nice to have?
Before we bang our heads on the wall any further, I suggest this discussion come to a pause as we try to contemplate why I felt that the bass performance of the JC1+ was preferred to the M10. It just seems pointless to speculate endlessly until this information is known, unless of course, you are into head banging. (It's what audiophiles do! Saves wear and tear on the ears.)