From a technical standpoint Richard's comments strike me as plausible. Which is not to say that using non-MIT cables will invariably blow up the amplifier, but it seems conceivable to me that under some circumstances either a full-blown oscillation or adverse sonic effects could result.
An amplifier that has extremely wide bandwidth and that uses feedback and that is driving a heavily capacitive load can easily turn into an oscillator. The Spectral's certainly have extremely wide bandwidth, although I don't know how much feedback they use. Keep in mind that the load capacitance is not necessarily just that of the cables, but might be the speakers themselves, if the speakers happen to have capacitive phase angles at frequencies that may be problematic to amplifier stability. That would especially be a concern with electrostatic speakers. The networks in the recommended cables presumably isolate the amplifier from speaker capacitance to some degree.
This paper pertains to op amps, but the basic principles it presents are relevant to any amplifier that uses feedback and is faced with a capacitive load. Note the reference to "problems such as peaking in frequency response, and overshoot or ringing in step response" that can occur even if the point of instability is not reached, but is approached.
Also see
this paper at the Spectral site, which also strikes me as plausible, at least for the most part (the exception being the references to time alignment, about which I am a skeptic in the context of cables).
Regards,
-- Al
