Very possible the Sonist is an easier load and more compatible with SET/SEP amplifiers than the Soliloquy.
Very true Charles, though if I recall correctly, Dennis Had had a hand in the development of the Soliloquy line of speakers. I seem to recall they were also manufactured in North Carolina, and Dennis helped design them so that they had a very stable, 8 ohm load.
In fact, here is a quote from a review of the Soliloquy 6.3:
Fixtures at every audio show I've attended, Soliloquy loudspeakers have a growing reputation among my ilk of audiophile -- tube lovers, that is. I understand that Cary Audio's Dennis Had designed the original two Soliloquy speakers, which have been long discontinued, and then sold the rights to the name Soliloquy to the current owner, Bernie Byers, who has bulked out the line.
Certainly, 93 dB is more efficient than 90 dB, but I wouldn't think that would be a night and day difference.
However, the proof is in the listening.
Cheers,
John