I recall seeing a foto of a very interesting amp that was to become the audio innovations 3rd audio, with a 211 valve.
BTW, for the uninitiated, its like an 845, but held to be a better valve.And the ongaku uses it. whilst a 2a3 triode gives about 4 watts, a 300b about 8, 211s can give around 20. I am currently running 8 watts into 87db speakers, and it goes plenty loud, so imagine what a good deal more.
These big triodes tho' need about 1000volts, so expensive transformers, and caps., I have had about 5 x 240 volt shocks, so far, and don't wish to go any higher at all.
There are even bigger valves that dwarf even 845s, perhaps running 3000 volts, and are used in the wonderful world of radio transmission and all that, of which I know sweet fanny adams., fascinating tho', a bit like old steam engines. a real pleasure.
check this out, the one on the right is a BIG valve, an 845, just imagine the monstrous on on the lhs, scroll down halfway.
http://www.welbornelabs.com/stuff.htm
Believe it or not, you can get an 845 amp of ebay, for aout £600

saves about £4000 for one of the emporiums, I very nearly plumped for one, but decided I had enough on my plate
Its a shame that 3rd audio never got off the ground and A.I. went the way of the dodo. Really great company. different.
Thanks for that hugely comprehensive potted history BTW. Very informative
Most of these big horns are 100db or more, to put that in perspective, you can use a 4 watt amp say with 103 db speakers, and it will be louder with 1 watt, than a 30 watter max out into 87 db speakers .
There is a school of thought that believes these really low power say 4 watt triodes are the best of all, and combined with big horns, there is nothing to touch them.no not even a naim 500 into dbl's