With the morden speaker, 1-2W is impossible to drive but with vintage speaker which has sensitive is higher than 96db, too much of power is not needed and 1-2W power tube amp is really impressed.
For years, I have been thinking that 71A is the best tube for amplifier that under 2W of power, although it has around 1W of power but its sound is really impress me much. A little dark, rich in mid low and very sweet. That is why, I like to use it for a driver tube in higher output power amp like 300B, 50, VT62 vv...v
Until the day I tried to use 205D for an amplifier driving my horn system, actually, I dont like 205D because it is too expensive. For a tube with little output, cost 1000USD for a pair is crazy, even a Psvane tube cost 600USD for a pair. I dont like to use expensive tube, all my amps, I always tell my customer, it is even good even you use it with China tubes, of course, if you have money, using America, Western Electric tube is very very good, but if you spend much of money for the amp and the parts inside and dont have enough money for an expensive tube, then using cheap tubes is good. In my opinion, the schematic, parts using in amp, skill of building is better than maker of tubes. You must know that Audio Note Kondo uses order made 211 China tube in their amp instead of expensive Elrog.
I make an amp which can be used 71A, 45, 305D to compare the sound amongs the best tube for mini watt amplifier. 45 is higher power than others, the sound is very sweet, beautiful and rich, but it is not as good as 71A, although 71A has around 1W of power, in 71A, a little dark of sound that 45 does not have although the detail 45 is better. Comparing with 2A3, 45 is much better although it does not have much power as 2A3 but 71A is better than 45. With 205D, the sound is even better than 71A, the detail and vivid of sound of 205D is the thing that 71A does not have but it the sound is dark, sweet that 71A has. It is really impressed me much. Ouput power of 205D is under 1W, although plate loss is up to 14W, it is very strange. In the datasheet of Western Electric, it is also said that if using for audio purpose, it should be under 1W.
If using a more powerful tube to driver, it may be reach to 2W of power with THD under 5% but this power is good enough. 717A is really good tube for such kind of amp.