2a3 ?

I have both! A Will Vincent custom- built 45 SET using Emcron output trannies; a 2A3 Sanei 560A with Tango power, choke and trannies from Japan. Neither in use because I sold my vintage Heresy's - the only speakers on hand capable of use with low power SET's. The 45 is only good for 1.75 watts at clipping; the 2A3 will do 3.5 watts. Subjective impressions of these two tubes is entirely dependent upon speaker choices. In fact the 45, 2A3 and 300B are most linear when used at 25% power. Past that distortion rises rapidly!

My speakers are 99 db/w efficient.  I own a pushpull 45 amplifier that works well with these speakers, but, I don’t play music that loud so I can’t say how happy others would be with my setup.  I have a parallel single ended 2a3 amp that also delivers sufficient power.  My favorite amp is a pushpull 349 (this is a very rare tube that, fortunately, has a long life when driven gently) amp that delivers about 5.5 wpc.  

I had a wonderful Tektron amp that used 45, 2A3, and 300b.  I think the 2A3 might have been best but it depended a lot on the tubes.  Jerry

I own the Coincident 300b stereo and am very happy and impressed with it. I did upgrade the tubes on my own.

There are fans of the romantic sounding midrange of the 300b, who will not listen to anything else, while there are people like me, who like the tube, but not as much.  You simply must listen to a variety of amps using the various tube types to make up your own mind.  

All of these simple triodes are most often employed in single-ended amps, but they work well in pushpull; the sound is different for the two topologies.  Pushpull tends to have tighter, punchier bass and a better sense of drive, but, single ended amps tend to sound more natural, relaxed and less "mechanical" sounding (the bass punch of pushpull can sound the same all of the time, hence mechanical, while single ended amp bass seems more subtly variable).  I like both types of amps.  As I mentioned above my favorite is a very low-powered pushpull amp, but my all time favorite amps (that I don't own) include an output transformerless amp and an extremely vintage pushpull amp that runs a 252 tube (variant of a 300b).