I'm contemplating building either of these amps from a kit. Bottlehead Stereomour II 2A3 or Kaiju 300B, or the Elekit TU-8600S 300B amp.
Good 300B tubes seem expensive, 2A3 not nearly as spendy. My speakers are very high sensitivity, so 2-3 watts for the 2A3 and 8-10 watts for the 300B is not...