List Of Small Company Tube Amps

These may not qualify because their owners/builders either passed away or no longer design, but if you can find them on the market, they're well worth the effort and price:

Herron Audio

LFE

Croft

+1 on Triode Corp from Japan. Well made and smooth sounding. 

@ronrags for some reason I can't reply to your DM so I'm responding here instead. I love my Cronus Dark. It was not an upgrade from a non-dark version. I opted for the Dark because I didn't want to be constrained in speaker choices, and it hasn't disappointed. Currently driving a pair of Maggie 3.7s and to my ears, the system sounds amazing. But the major caveat is that I don't really have a point of comparison as this is my first system. I worked with Mike Hoatson at The Listening Room in Chestertown, MD, and he would be much more capable of articulating the benefits of the Dark versus the non-Dark in terms of sound. Good luck. 

Raven Audio +1 USA out of Texas

I have  tried and owned the Black Hawk tested and owned Osprey for 5 years and now own a Reflection with Corvus Speakers and their cables and not one time disappointed with equipment and Dave Thomson sure knows how to select tubes to make these Amp sound beautiful. Highly  recommend

One of my favorite tube amp makers is Synthesis.  They consistently make amps whose sound is WAY beyond one's expectation for the price.  My two favorites of their lineup are the integrated amp/DAC combination--A 40 (twin KT66 tubes pwer channel) and the A 100 (four KT 66 per channel).  

I own custom tube gear made by a builder in Italy, Aldo D'Urso, who has made a dazzling array of gear--he builds his own DAC, phono stages, amps, linestages, field coil power supplies, Western Electric horn reproductions.  For some gear he winds custom transformers.  His originals and reproduction/rebuilds of Western Electric gear is amazing nice sounding.