Very good points yaluaka. Every component choice involves some kind of tradeoff, and if low-powered SET is your thing, you either live with some compromise on ultimate volume capability or a MUCH more limited range of speaker choices. The right sonic choice depends on a wide range of variables and one should not limit the candidates by the type of tube, or for that matter the topology--single ended triode is NOT inherently better sounding than pushpull or output transformereless, etc. I own a parallel single ended 2a3 amp, a pushpull 45 amp, and a pushpull 349 amp. The parallel single ended 2a3 is, by far, the most expensive and it is terrific sounding, but, to my taste and in my particular system, the pushpull 349 is the best overall. If I had to pick the best amp I've ever heard, it would be a custom built OTL amp or the Western Electric 59B amp (pushpull 252 tube that is an ultra rare and expensive tube similar to a 300b).
After hearing many amps employing these tube types, I do come away with some very general observations about tendencies, although there are many exceptions. The 2A3 tends to be leaner sounding (not as much warmth and upper bass) than the 300b, which also means it has a clearer sound and it has very good dynamics and has tighter bass as compared to a 300b. The 45 is very nicely balanced and has tight bass, and sort of lies between the 2a3 and 300b in terms of midrange warmth. There is something "beautiful" about the midrange for the 300b. It has a very warm, comforting sound, but, it does not have quite the dynamics and lively sound as the other two types. I've heard pushpull amps that are very similar, by the same builder, employing all three types, and these rough characterizations come through. No particular sound is "better" and much depends on the speakers being use, the room acoustics, etc.
