like anything else, it is useful to understand what we are dealing with factually - and in specific terms -- when it comes to driving speakers, and here, specifically maggies
maggies, big and small, are 4 ohm, purely resistive loads (meaning there are not torture chamber drivers/crossovers with their difficult electro-mechanical resonances that an amp has to deal with - large doses of inductance/capacitance - i.e. phase angles the amp must see and deliver its modulated energy into)
as such, the megnepans are not particularly 'difficult' loads to drive (impedance does not fall well below 4 ohms, amps sees a pretty simple resistor ahead of it) but the amp does need to deliver alot of current (flow/volume of energy into that load) into it to activate and control the substantial mylar panels
there are (and have been) famous torture chamber speakers like big thiels, focals, acoustats etc where impedance drop to 2-3 ohms in the bass region, and with great reactivity - magnepans pose none of these challenges -- but maggies do need strong current delivery (and thus excellent power supply design/strength and control on the part of the amp) into their purely resistive 4 ohm load
it is helpful to know what one is dealing with, and then get the right tool built for doing that job
