Japanese tube amps. Wavac, Air Tight, Audio Tekne, Komuro etc.

Air Tight is very highly regarded, but probably gets more discussion on sites other than Audiogon, just as do other highly regarded tube amplifier brands, thinking Jadis, VAC, NAT, Nagra, Margules. Air Tight enjoys a reputation in tube amplification similar to what Accuphase enjoys in solid state.

Yes, many high end brands are not discussed here or discussed very little. I don't know why. I can understand that not many have one of those Japanese amps or Nagra but still. Even VAC and Lamm are rarely talked about. Accuphase, Gryphon, Soulution etc, - sometimes but again not much. They are all expensive and very expensive equipment, of course, but I don't think that's the main reason.

Add Aesthetix to the seldom mentioned list. Top quality stuff.

I owned an Air Tight ATM-2, which was used to drive Harbeth SHL5+ speakers. It was the best tube amp I've ever owned; the sound and build quality are exceptional. 

I'd love to pick another ATM-2 up someday, but you rarely see good quality units on the used market.