List Of Small Company Tube Amps

Rogers High Fidelity sells demos (with full workup and warranties) on Ebay at decent prices.

I think VAC qualifies as small, though expensive/high end.

Actually maybe a better question would be a list of large tube amp making companies? Aside from maybe Luxman I can't think of any. And please don't say ARC they were just recently sold for almost nothing.

+ 1 for Had. I've owned a Dennis Had amp since 2017 and it still amazes me how good it sounds. A hand made masterpiece, a "lifetime" amp.

+2 for Dennis Had’s Inspire amps.  He designs and hand builds KT-88’s, 300b with WE tubes, and more recently 2A3’s.  $2k-$5k.  Goes by radioman731 on ebay.  If you can pick up locally in Cary, NC, he’ll buy you lunch, introduce you to a couple of his audio tubehead buddies and give you a tour of his workshop, The Toy Factory. Where I first saw a pair of open baffle speakers he built for his studio, they’re all the rage now. Superb low watt SE amps . Have one of his KT-88 Firebottle’s. He put a volume pot on it for me, so nothing between digital source signal and high efficiency speakers, very clean, super low noise floor, and layered soundstage. 
 

Also his former firm he founded, Cary Audio, most under $10k.  Have one of their 1990’s 300b LX-20 I picked up used for $3k. Sent it to Cary for a shake down, replaced one burned up resistor. Great service, very quick and reasonably priced.  The LX-20 is a SET that runs KR 300B XLS tubes to 20wpc, pretty amazing. Designed by Dennis. I’m obviously a fan of his work.