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

Well are 100db if that doesn’t work for 45…

@superelmar exactly! You need about 6-7 dB more; type 45 amps are better suited for headphones.

I have transformers in my inventory for a 45 amp, as well as a 2A3 push pull. 
 

I look forward to getting them built and comparing them. 
 

As stated above, I would be looking into a PP 2A3. Very curious about how tyt would sound. 
 

I use a DIY SE EL84 with my Cornwalls and it drives them with comparative ease. Now, I don’t play particularly loud, and I’m not a bass head, so others may not find that satisfying. 
 
Do really like EL84’s, I do :) Listening to a pair of UA-1’s now, and even in their poor state (just got them) they sound quite lovely. 

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.