I also think it is extremely important with Maggie based systems to address RFI/EMI issues in the entire system. It is my belief that Maggies somehow reveal the high frequency grunge caused by these issues to a greater extent than most other speakers, resulting in high frequency related listener fatigue. This can, I think, sometimes be interpreted by the listener as an overly aggressive top end--too bright. The ribbons, and even the quasi ribbons, are very revealing. If something is wrong in the high frequencies, you are going to hear it.
One probably does need to treat the room for Magneplanar speakers but it's for the wrong reasons - the reason that these speakers appear to have an "overly aggressive top end--too bright" & "The ribbons, and even the quasi ribbons, are very revealing" is that, basically, Magneplanar speakers are not time-coherent speakers.
This is very clear from the measurements Stereophile has published for the MG3.6/R - see Fig 6: step response:
http://www.stereophile.com/content/magnepan-magneplanar-mg36r-loudspeaker-measurements-part-2
and for the MG1.6/QR - see Fig 5: step response. Here even the published text clearly states the speaker is not time-coherent:
http://integracoustics.com/MUG/MUG/reviews/stereophile_mg16qr.htm
Non time-coherent speakers have the (very) bad habit of letting the listener hear the high frequencies before the mids & the mids before the bass. As a result the sonics are tipped towards the high frequencies & you get these sort of comments: "sometimes be interpreted by the listener as an overly aggressive top end--too bright. The ribbons, and even the quasi ribbons, are very revealing".
Making Magneplanar speakers time-coherent would resolve the issue but this has to be done at the design/factory level & not in the listener's room after the fact they are purchased by the user.