Yes, I'm referring to single tube SET, with my statements. All others are simply parallel configuration to lower output impedance. As Albert Porter once described it to me, parallel is like a choir singing, and single tube is like a soloist singing. No matter how syncronized a choir sings, it will never be as clear and articulated as a soloist. I thought that was a very lucid description. I think the simpler the better, as long as it can get the job done. Of course, there are certain speaker requirements for efficiency in order to use low power single output tube SET amps.