I don’t know if Coincident qualifies as small since it makes a complete range of audio components and is probably best known for its high efficiency speakers, but it sells direct to consumers (no dealers) and looked a bit like a one-man operation when I visited the Coincident room at an audio show years ago, with designer Israel Blume and his wife the only ones representing the brand. I remember it as the second best sounding room at that show, behind only the room with much more expensive Kaiser Kawero Classic speakers.
Coincident makes two very reasonably priced tube amps for high efficiency speakers, the Frankenstein 300B stereo amp for $2,500 and the Dynamo 34SE MKIII integrated for $1800. Most of its other tube components cost less than $10K.