2a3 ?

I have heard some SET amps running the big transmitter tubes, including a 1610 tube, and I have not heard any that surpassed the lower powered SETs when playing speakers of high enough efficiency such that no amp was being forced to play out of their comfort zone.  Yes, some 211, 845, 833 amps sound pretty good, but I still like the 45, 2a3, 300b amps a bit more.  

I never ran my parallel SET 2a3 amp into hard clipping, but, I did suspect it was slightly compressing peak volume when playing certain kinds of music.  This appeared when playing large acapella choral works at somewhat high volume--no obvious distortion but the music sort of stopped getting louder at peaks (99 db/w speakers).

I don't agree that, even with very efficient speakers, SET amps always win over pushpull.  There are certain pushpull amps that deliver the same sort of natural, harmonically dense and complete sound of good SETs, while sounding a bit more punchy and dynamic.  There are also contenders from a completely different camp--the output transformerless (OTL) amplifier.  The incredible dynamics and liveliness of good OTL amps can be extremely captivating, and they deliver this kind of sound without necessarily being bright or harsh.  I don't think any particular topology beats another; it is a matter of taste/priorities, system matching, and specific execution of the topology.

I have been told by someone who should know that a 2a3 is, essentially, two 45s in one enclosure. When I used to own a 300B amp I was always a bit puzzled about the reverence shown to the 2a3. I wondered why praise of the 300B was not universal? Why was it often considered as "behind" the 2a3 and the 45?

Then I got to hear the 45. The midrange emphasis of the 300B was clear, as was the more extended frequency response of the 45. The tone and inner detail of the 45 was breathtaking (my room, my speakers, my listening preferences, YMMV). 

So, not exactly a response to the OPs original question, but I wanted to add my .02...

Nearly pulled the trigger on 45 amps as well but concerned

about availability/durability/reliability of tubes that haven't been manufactured in decades. I have little tolerance for equipment that

may have questionable reliability.

I love the 2a3 tube I have a pair of George Wright monos myself and love them. Clean and clear sounding but still natural and warm they drive my Audio Note AN-J's perfectly.

Very much looking forward to reading people’s experiences. I recently picked up a Sony TC500a R2R portable player. Bought it to harvest the transformers and the speaker drivers. 
 

Trying to figure out if I want to build a 1626, 45 or 2A3 with the transformers. 
 

leaning towards the 2A3/45 option.