Watts! How many do we need?

Enough to cause a brown-out in your neighborhood at will. 

@pindac
Thanks for the detailed description  of your experience and surroundings where this demo took place.
That is indeed a very impressive performance from a 3W valve amp.  It is very encourging to know that there are new valve designs in development which may change the way we experience audio.
Hope this product will be made  available to all to evaluate, purchase and enjoy in the near future!

@larryi 

If watts tell half the story, which advertised spec of the amplifier is a better indicator? I understand amp x volts = watts. However, based on my basic search, amplifier specs don't advertise/disclose this info.I need one more variable.

However, based on my basic search, amplifier specs don't advertise/disclose this info.I need one more variable.

@tee_dee The variable that tells the most about how an amplifier will sound is distortion vs frequency, which is a chart with a curve on it. Ideally, the curve is really a straight line across the audio band. If it rises with frequency, this can cause the amp to sound harsh and bright. The lower the frequency this happens, the more harsh and the more bright. The brightness is not a frequency response error, its caused by higher ordered harmonics being audible. The ear interprets such harmonics as 'bright' and also 'harsh'.

But you are right, many manufacturers do not publish this particular measurement! I'm of the opinion they really don't want the spec sheet actually telling you how the amp sounds.

I don't think that I would ever buy any amp based on advertisement, published specification, review or internet buzz because none of that seems to match my own personal preferences when I do get to hear the gear.  I don't go crazy trying to hear everything; through long experience, I generally know what kind of amps I like and should bother to audition.