Minimum 8 ohms

Ask Nelson Pass.

Around 1986-7 at an audio store that sold some nice stuff Denon, Bang&Olufsen,Klipshorns,Nakamichi etc.I overheard a salesman call the PA5 and PA7 amps wimpy.I never had one and I dont know why he said that.I too always heard the designs from Pass were good into very low impedances.Just another story,doesnt mean much,YMMV,Bob

Threshold Stasis gear are good into lower impedance loads, but that's a bird of a different feather. Nelson Pass sold a concept, not Nakamichi's. A great idea, poorly implemented, doesn't necessarily make great gear.