another consideration is using Martin Logan SL3 speakers. these are true electrostats,and although many of us have used the Ice and latest design class D amps with 4 ohm speakers, including Magnepans, and have had no problems, e-stats are notoriously more difficult because they can have ultra-low impedance dips, 1 ohm or below even. Even tho they are less efficient and need more power, Magnepan planars, OTOH, their impedance is mostly resistive in nature at or near 4 ohms throughout the freq range, which is an easier load.
I checked the SL3 specs and they are 4 ohm rated (of course) but have a low impedance dip to 1.5 ohms at 20 kHz. 1.5 ohms is pretty low, even for a THX U2 certified receiver. Ultra 2 means reliable to 3.2 ohms I believe. If a particular soundtrack had enough energy at those hi freq's or the preamp or amp were clipping, producing hi freq harmonics, at loud enough volumes, it's possible....
further, if the above poster with the blown gear set the M-L's at Large, since they are spec'd to hit 30 Hz, he just may have taxed the internal amp or preamp in the SC-68 to its clipping limit. all this is pure conjecture, of course.
I think there were a couple, maybe not very many, M-L e-stat owners that posted in the Ice amp models but I certainly don't know if any were in the SC-57/55 thread, which was 1st model with the new IR amp design.
Sorry to hear about any gear loss but other than speculate, I certainly have no hard answers
IMO, while Maggies can be driven by Ice and the new class D amps, I'm not sure if trying to drive full-range e-stats, especially if they were set to Large is a good match with the receiver's amps
. I do think adding the ext amp was a good move for these particular speakers.