Presuming I have a sympathetic pair of loudspeakers to mate the amplifier with, and admitting to being willing to live with the inherent tradeoffs of the marriage, I prefer the lower power SET amps. There is a certain magic there that I feel the larger tubes cannot match.
Totally agree. For me, the secret is the "sympathetic speaker" plus a good circuit design of the SET amp using 2A3/45 or a 71A.
Personally, my understanding is that the magic happens because distortions are avoided. Distortion is directly proportional to the amount of power use. Why go SET and then go high power? I really think that its beating the purpose already. When you go above 100 dB sensitivity drivers, you will find out that you do not need more than a2A3/45/300B tubes to drive it. My honest opinion base on my system only..