Ultralinear vs. Triode vs. SET

For my taste, a speaker well matched with an OTL is the very best type of amplification overall, especially if you include compatability with a broader range of speakers than is possible with most SETs; and much better frequency extension with very resolved midrange. If you are intrigued with SET, a good time to also consider OTL (Atma-sphere, Joule, Transcendent, and soon Music Reference - there are others).

IS there any consensus (not kidding:)) that for a given circuit, fewer output tubes always sound better than more IF there is sufficient power to drive the speakers? Maybe it was Sam Tellig who once said that some of the best sounding tube amps tended to be 40-60 watt tube amps, most if not all with just a pair of tubes per side, I wonder how important that is and whether running 2 pairs per side makes it that much harder to get the "purity" of sound you get with a single pair (or just one output tube). Again, assuming the lower power rating does not present an issue for driving the speakers.

What two-tube per channel P/P true pentode amps are there in current production?

Thanks Ralph, that's what I meant to ask about "pentode"
operation. By the way, can someone explain tetrode [?]
operation - I often see that word used. Is this yet another
possible tube application?

"The ability to put power into a loudspeaker often transcends WPC or the loudspeaker's published sensitivity and impedance specifications." Amen.

I noticed this when I finally decided move from the 8ohm tap to the 4 ohm tap of my Music Reference RM10 MKII (Ultralinear P/P. A/B) to drive my Merlin VSMs. I thought I was on the lower limit of power (35watts) to drive the Merlins, though plenty loud! By switching to the 4ohm tap (light loading), the power was reduced by 20% (down to 27 watts), yet darn if it did not sound better, had better, more articulate bass, and better transient attack. Perhaps fewer watts, but apparently less distortion, and more current available for transients. The amp was more in sync with the speaker.