300B or 2a3 SET Class A for Heretic Model A?

It always bothers me when some asks about a lower power tube amp and someone chimes in with, get a higher powered amp. To me if you want a 300b, 2A3 or 45 amp get one. I have all three. I listen to music all day and at good volume and one room is 1400 square feet. These amps are the best, and at the same time there is a culture around them. The people who espouse the more power mantra are not part of that culture and are irrelevant if you really want a low powered tube amp that’s about sweetness and musicality and tactile-ness. And I’m sure many people feel they have this with their un-low powered tube amp set up. Good for you. But what I'm talking about is not what everyone wants and that’s totally fine.  It would be silly to want a historic style 300b amp and its ilk and not at least have the experience that got you curious about one in the first place. It’s a hobby, try things doesn't really help to ask questions. Just experiment and sell on what you don’t like. It will still be cheaper than golf or wine. There are no right answers and crazy little accurate information. Everything in this world is personal. 

I’ve run 845 SET amps (Antique Sound Labs, USA) and been very satisfied with their 27watts per channel.   Very quit, lovely midrange, tight powerful bass and extended highs.   Great imagine and overall tonal quality.   They matched well with my electrostatics.   If you are concerned you need more umphf, then you might consider a SET based on the 845 tube.

Another 2a3 fan here it has a clarity and a speed that 300B doesn't have, to my ears at least.

Again don’t listen to anyone here, me included😂

With all due respect to others here, you don’t need a higher power amp, and a 2A3 amp is or is not better then a 300b, there is no such thing in this world as better. Every time you change your speakers or your amp, you’ll have to decide if you hit on the right equation. If you didn’t hit on the right equation it’s not the amps fault, it’s just that situation. I had a 45 amp that didn’t sound good with the Altec's I had, didn’t sound good with Tannoys, and I just put it aside and one day tried it with some speakers I was using at work and bingo. Again it’s a culture.  It’s a tremendous fun little corner of the high fi world. And if you get into deep enough you’ll find yourself looking for copies of Sound Practices magazine. 

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.