Eniac, yes I certainly agree that Cardas (and a number of other manufacturers) are to be commended for providing meaningful information about the design of their cables. Unfortunately those manufacturers seem to be in the minority. And while in general such information will of course not enable one to predict how a given cable will sound in a given system, at the very least it may allow some cables to be ruled in or ruled out from consideration, especially if longish lengths are involved (since most cable parameters are proportional to length). And it can provide confidence that the cable is not simply designed to sound different by virtue of having bizarre electrical parameters. As well as providing confidence that the designers have a good understanding of what they are doing.
I believe my speakers (Magico S3) would indeed fit the bill you describe
in terms of low Impedence nominal and even lower as the Freq increases.
Since the impedance presented by an inductance rises in proportion to frequency, and in the case of a speaker cable that impedance will assume increased significance as it becomes an increasing fraction of speaker impedance, in general that kind of speaker will be more sensitive than average to cable inductance. And lower inductance will work in the direction of providing increased extension and detail at high frequencies. However in this case I suspect that is not what is making the difference, because the inductance of the Mogami cable was also fairly low, by virtue of its short length.
What seems more likely to me, although without having knowledge of and analyzing the design of the specific amp it can't be said with any certainty, is that the 2780 pf of capacitance presented by the 10 foot length of Cardas Clear may to some degree have caused a resonant peak in the frequency response of the amp at certain high frequencies. Perhaps in the ultrasonic or RF region, but with effects on audible frequencies occurring as a result of phase shifts and/or intermodulation effects.
If so, a length that is considerably shorter than the 10 foot length of the cable you evaluated wouldn't necessarily provide similar results, even in your particular system. But as you indicated, it's also certainly possible that neither of these parameters had anything to do with the differences that resulted.
Regards,
-- Al