I've owned a Had Firebottle HO (allegedly "high output") for years and it's brilliant, and handles pretty much any power tubes of the "KT" variety with aplomb...most recently KT66s for some inexplicable reason. Got it barely used for around 1100 bucks in early 2017, and it's signed by Dennis as built on 12/01/2016. A thing of beauty that really shines with efficient speakers like my Heresy IIIs. I swap it out for my current fave (a Pass XA-25...tubeless but also brilliant) from time to time if I feel sorry for it on the shelf.
New Dennis Had amps
Dennis Had was the chief engineer/designer at Cary audio and is responsible for bringing back single ended amps in the US. Since his retirement he has been making boutique amps and selling them on eBay when he has one to sell. The Firebottle KT-88 is a single ended pentode amp that can take a huge variety of tubes. I love mine. He has also been selling a 300b SE amp. Looks like he has a bunch more models in the pipeline.
https://www.audioaficionado.org/showpost.php?p=1068202&postcount=7125
There’s a huge range of prices ranging from the $1500 “Kleen Sweep” using what looks like 6bg6 tubes up to the $8500 PSE 300b amp. There is also a SE 46, 6v6, and even a 7c5 amp in the mix as well.
It’s so nice seeing someone building for the love of it. He only builds what he likes and doesn’t need to make a living at it. Truly every DIY builder’s dream:)