Hello, Michael. I am glad you are here.
"If you have ideas on low power, sweet sounding amplification in kit form that adds a few hundred bucks to my previously cited budget, I’m all ears."
The Jerry Curtis 'Spudkit' has received many good reviews through the years.
https://spudkit.com/?page_id=198 Approximately $400 depending on options. He is waiting on parts at the moment, details here
http://spudkit.com/?author=1A high efficiency 12 inch such as the Ciare NDH12-3, plus a 1.4 inch horn driver, maybe the Beyma CD14Nd interest me to make a high eficiency speaker with an impact type of sound. Each is about $250 at US Speaker, plus another $120 for ready made horns for each compression driver. Both Beyma and Ciare make horns that might be top notch for this driver.
I don't know what cabinet, maybe an ultraflex similar to the Decware NFX, or the Decware Pro-12 guitar cab (but probably bigger for Hi-Fi use), or the Supravox ultraflex. Or probably a hundred other cabinet designs. Something to get some Bass emphasized if using a 12" that is designed as a midrange as this one is. I like the idea of using a 12 mid instead of 12 bass as I think this would give a clearer sound. But then the builder has to get his bass some way or other.
Perhaps that is helpful, who knows?
Best wishes, Brian