Sorry, long TLDR: try it 
Sounds like what I just went through. I also had an "itch" I had to scratch, I picked up some 98db speakers, which were designed/voiced with a 300b amp (also built by the speaker manufacturer). I am sure if I posted as you did looking for suggestions I would have received several "don’t try a 45 tube amp, no where near enough power" so I didn’t post- I just went ahead and did it based on plenty of other reviews/anecdotes that stated that the 45 tube was the best of the bunch, and I’m glad I did it! It is off golf season and I am retired, so I generally surf the internet researching what many have done/known/experienced and posted for about 50 hours a week.
First I appreciate very much @atmasphere posting on here, and filling the threads with his vast knowledge. He of course has had plenty of negative posts I am sure over the years, more than enough for most manufacturer’s to bow out of the forums and vow to never return. (Reminds me that it was "refreshing" to read what Charles Hansen had to say years ago (RIP)). And the internet seems to be getting more negative by the day- more and more "expert" opinions and less and less facts; not just audio forums but in general. Absolutely Ralph has forgotten more about amplifiers than I will ever know, and some of what he wrote above is over my head, but it is nice to have those who do this audiophile thing for a living post their knowledge so that some of us can digest it.
Having said that my latest experience contradicts some of what he has said. But first, as some have referenced above, how loud do you listen? The World Health Organization suggests at 95db one should only listen to music for just over 1 hour per week. 90 db and you are good for 4 hours per week. I don’t know about you but I want to listen for much longer than that, and more importantly I want to retain what hearing I have left, so I can enjoy this hobby more many more years. (Interesting in that I have noticed a few ads on Audiomart in the past few months where someone is claiming their reason to sell is due to hearing loss)
Even at 80db SPL WHO suggests 40 hours per week. It is unclear if that is total, or just "work SPL". If someone mows their lawn twice a week without hearing protection, uses their Vitamix daily, watches a movie on their home theatre with peaks at 95db etc. well now perhaps you can listen for 30 hours a week? I have been listening to my hifi for 12 hours a day. Right now I am playing Tsuyoshi Yamamoto at 50db. At night I might have peaks of 80db but that is as high as I will take it.
So for me, why bother paying attention to a spec of "50 watts required for 95db" when I will never get there?
Using those same numbers that is the same power of:
25 watts for 92db, 12.5w for 89db, 6.3w for 86db, and 3.2w for 83db.
Knowing this, and I also have a smaller room for this experiment, I took a plunge on a Yamamoto A-08s 45 tube amp (no relation to Tsuyoshi ), and it surprised me how loud it goes! My 98 db@1w speakers are a nice flat impedance curve (I am told) which is easier to drive, yet they are 4ohms I believe I am getting not 2 watts per side but more like 1.7 wpc? And it sounds glorious! At this point I don’t see myself ever selling this amp. I have a 300b on the way (shipped today!) as well so I will rotate amps around for a "saveur du jour" as if I use one amp for half the time the tubes will last twice as long, please correct me if that math is wrong. And the bass? Or a lack of it as some suggest one will get from a little flea amp?* Please, travel to my house and tell me there is lack of quality bass here: There is not- it is perfect- deep, rich, taut but not too tight, tuned and awash with texture, gradations and nuances -absolutely perfect -as long as the recording was of sufficient quality. And in the 3 weeks I have owned this little amp I have yet to max it out, so at 75db listening average I am probably using less than 1 watt per channel- amazing!
Interestingly, even some older pop and rock recordings surprise me with the quality and details of bass guitars and drums that I have never heard before. Looks like some of the reviews of this amp from over a decade ago were accurate: It is one hell of a little amp. I don’t know if I just lucky with a good matching with my speakers and others don’t get the same result, I don’t have that knowledge. If there are "weaknesses with a SET" they have not been apparent to me yet.
On top of my excitement on the sound quality it is gorgeous to look at, and the point to point wiring is so precise it demonstrates the amount of care and passion Mr. Yamamoto puts into his products. He manufactures virtually every part of this amp by hand. Beautiful.
And if you are wondering what I was listening to before the Yamamoto it was a Coda 15.5. Bass may not as powerful as some, but surely not lacking. I am still keeping it as it will be the high channel amp for my Magnepans.
*One other point worth emphasizing, and I see you have tube amps already so you probably are aware, but you and I both did it here in this thread: Stating all 45 tube amps, or 300b amps are in the same class is incorrect. You might have read the same claims that I have: "300b tube amps have great mids but wooly and have no bass", or have rolled off frequency response, but what they aren’t telling you is they have or have listened to the bottom end quality of those designs. As @larryi stated above the quality of the output transformer will have a huge impact on the quality of the bottom end, and I assume other frequencies as well.
Funny that if someone posted that they don’t like transistor amps because they have a brittle and shrill top end everyone would jump on that poster and ask which one specifically he was referring to- but in a tube thread only very few state the same response, and most assume "a 300b tube amp is a 300b tube amp".
So there is my flea-tube amp journey so far. Not much kit-info for you but interestingly the Yamamoto was available as a kit. Personally I would not buy an amp from someone who learned how to solder on a tube amp kit. The money you would save buying it you would loose on resale. As your room is not too much larger than mine and if your required sound pressure level is reasonable I say give it a go! Only one way to find out!
