Best Tube Amp for High Sensitivity Speakers: 45, PX25, or 300B?

Thanks Jerry.  Appreciate the advice.  Looks like you are heading in an interesting direction with the AD1 tube!  Would love to hear your review of it after you've had it for six months.  I do have a budget; wish it wasn't so.  Yes, I've looked at the new Decware 300B.  I'm sure it is a wonderfully designed and built 300B, esp. as an integrated.  I am still debating the strengths and weaknesses of it compared to the other two tubes I mentioned.  It would be an easy default if 300B is the final choice.  Thanks.

auroravengeance:  The Lab12 looks nice.  I wouldn't know how the sound and dynamics compare with the three tubes I have mentioned.  Would love more input about the KT170's in the context of the others. Looks very nice and good price.

elliottbnewcombjr:  That would probably be the best way to go. However, I do know there are quite a few 300B mono blocks, but I've not seen a single example of the 45 and PX25 doing the same.  Those tubes get such high marks, it would seem like a good path, but I'm not an engineer.  The tube amp systems that run in the tens of thousands never employ them... There must be a reason.  I do know that some of these run hot, but that's speculation.

Thank you, Jerry.  You've effectively brought it back to the parameters of my original query.  I wanted to find answers to comparing low-watt valve systems and what the community thinks about these different valves.  I reduced the valve listing to three for a reason; I didn't just want everyone to tout their amps.  I already have a nice Swiss-Army valve amp.  I wanted to fine-tune the question to specific, high-end valves that render extraordinary clarity, dimensionality, breathtaking musicality, and live tangibility that the best valves can produce in conditions that can best employ them (high-sensitivity speakers). I lived in Europe (mostly Spain) for twenty years, studied production with the BBC under Queens College Cambridge, loved the British sound, and built a media company in Spain.  When I sold it all to return to the States, I hoped to one day reach that level of vicarious, tangible music listening that would exceed the most memorable moments in my past professional life.  This is my "end-game" system.  I am building a room just for it (as many here have done).  I am not as interested in thundering power as in palpable envelopment. Music takes me places, on journeys. For a special moment, I am with the creators and craftsmen as closely as possible. They are with me. There are special tubes that are sweeter, more sensitive to the nuances of music than others. I'm on that search for the right balance between dynamics, musical depth, and analog believability as many of us are. And like many of my forum compatriots, I don't want to poorly spend my precious investment on frustrating experiments and regrettable explorations.

I would like to thank **everyone** for some great entries and advice. I know this website has its detractors but in my year of involvement, it has been a great source and I've meet some amazing people in this community. Since starting this thread, I have been disconnected due to demands and am just now able to respond.  I've read the whole thread and reread it. I want to thank all of those who have added specific suggestions, brands, and models of tube amps that have been yielding good results for you.  There is also a treasure trove of good info you have shared on tube amp science--much of which I am just now beginning to understand.  From the thread so far, I have been immediately influenced by your advice on putting my simplistic goal of the best-fitting amp into a much broader understanding of the tube amp's strengths, weaknesses, and the many alternatives that go beyond what I narrowed my list down to.  Honestly, I am revamping my thinking on what my options might be. My budget does determine what I can consider (as for most of us).  I think I am looking more to "stair-stepping" upward from my current amp (PrimaLuna 400 EVO) to something that provides moderate, reasonable gains without breaking my bank.  I will have a lot more that I can spend in a couple of years when I unload a business.  But for now, I have to settle for only moderate improvements... the best bang for the buck. Again, thank you for your participation.  Hopefully, many are reading this thread and gleaning from it as well.  👍

liquidsound  John:  That BorderPatrol is a beautiful unit.  Out of my current budget but could be a bucket list amp one day.  Thanks for sharing.

Markusthenaimnut:  I think you are right.  I failed to give proper disclosure from the beginning of the thread:  exact speaker specifications, exact room dimensions, exact distance to speakers and, finally, average decibel listening of what genres of music.  I know all that could / would affect answers and opinions here.  

At any rate, the wealth of information continues to grow.  Thanks everyone. Your participation is being heard and it's a help to many!

kennyc:

Yes, I was looking for integrated at this stage of the game as it would probably be more within the current budget than separates, cables, etc.  Also, space issues where I have my sound system located.

My goal has been to learn from this system so that a major upgrade in about 2 - 3 years would be sussed out.  We are renovating an old farm in the country. I have a room that I'm renovating to be a dedicated music room, larger than the office where I currently have my system.  In my current room I have limited space with a pair of Daedalus Muse speakers.  They are sweet and demand little and I am not pushing them at all.  I will be upgrading to either a larger set of Daedalus or moving to a pair of Coherent 18's.  Both are reasonably high-sensitivity speakers but might require a different amp system at that time.  I'll have a better budget then as well. 

clhs04:  I believe there's some truth in that. I think most sound systems, environments, and demands do not fit the 300B ability.  Perhaps for the 20k+ 300B amps, there is a window to perform better, but not the low-budget systems.