Check out the "Teresonic" website. Also "Sonist", and "Decware".
"Reference 3A" is also a candidate, but not for 2A3 unless in a small room and you like simple music,300B would be fine. The trick is to find not only a sensitive enough speaker, but one with a simple crossover or better yet one with no crossover such as the Teresonic. Also the impedence of the speaker should be smooth and not go too low.I heard the Teresonic's top of the line speaker hooked up to a 2A3 amp and was totally blown away, especially the bass output was incredible! I think that the retail price of that speaker was under $15000.00. I have the Sonist Concerto 2's and I'm running them with about 5 watts in a small room and they will get real loud!
You should be looking at speakers with an SPL rating of 95db- 1watt@1meter or better. Good Luck and have fun!!