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

Try something different like the 211 tube ,or 845   More then enough power and sound very nice 

https://caryaudio.com/products/cad-805rs/

a dedicated line yes awg 10 if possible , and as I did 4 wire one a common ground 

the other ground a isolated ground in its separate path connected to its own grid to ground more monies but worth it you don’t need to isolate the digital after this .

buy a very good Ethernet switch , depending on your budget the   SW8  only $600

or top of the line  innuos $3700. Depending on your dac and quality of your audio system  what you can afford , the AC outlets buy quality Gold over Copper Furutech  or another name brand ,even Pangea $100 AC outlet very good . And on router for sure a 12v minimum 4 amp Linear Power Supply , any gsrbage wall warts need to go $5 junk noise makers , little green computer sells for $299 and never use stock power cords ,at minimum on the LPS power supply a Pangea Sig MK2  for example  I even put a synergistic purple fuse in the LPS as well as the upgraded Ethernet switch , each one  small but important  improvements ,

and Ethernet cables cannot be low end or your streaming will suffer, this too applies to the USB cable. Everything counts , I am still working on upgrades  last 

your dac , to me as the source how much can you spend $$. Myself semi retired have to save for more expensive items , the T+A 200 dac  I still have a few months to go to save , is imo and many others dacs we have compared it to directly in our multi state audio get together for its $7200 price a true bargain it beats anything under $15 k and more and has HQ player built into the platform to give you the ability to find tune this to your audio system ,to make it better still. 

I think the OP is mistakenly ascribing personality to the 45, 2A3 and 300B valves. What matters more is the circuit design and parts used. I have a 45 SET custom-built by Will Vincent (autospec) on an ST70 chassis that turned out beautiful! Plus a Japanese Sanei SA-560A 2A3 SET made with Tango iron. This I won at an eBay auction from a Japanese seller. It is the quality of the whole amplifier - the gestalt - that elevates the performance rather than the specific tube type!

I like low-powered tube amps of all designs--pushpull, SET and OTL--so I am not so wedded to a particular design.  As jasonbourne71 stated, it is the particular design and parts used that matter most.  In particular, the output transformers and interstate transformers (if used) that matter a lot.  

I do have some tube preferences (meaning I've heard a number of good amps made with a particular tube type), but it is not absolute such that I universally prefer something made with that type of tube over others. 

Of the three small triodes mentioned, I tend to most like the 45 as long as it is used with suitable speakers.  I own a parallel 2a3 amp that I used with 99 db/w efficient speakers and a 45 pushpull amp (both have sufficient power for my purposes, but then again, I don't play the system very loudly.  I currently run a pushpull 349 amp (5.5 watts per channel) that I like a lot.  I tend to prefer the 45, 2a3, 300b over the larger transmitting-tube SET amps (211, 845) although these can sound very good.  For pushpull amps, I also like a number of old and new designs that employ 6L6 and KT66 pentodes.  For really exotic tube types, I like the 350B, 349 (pentodes) and the 252 (triode somewhat like a 300b).

For the OP's 96-97 db/w speakers, it might be possible to use the three triodes mentioned (particularly the 300b), as long as the owner is willing to accept some restriction on very high volume listening.  I personally feel that some compromise in that area is worth it.  For a safer bet on compatibility, something in the 40 watt range should be sufficient.  

Look for a Dennis Had Inspire 300b. He builds each by hand one at a time, essentially made to order.  Sells on ebay under radioman731.  He built me a KT88 last summer, added a volume pot so I can stream directly to the amp, then straight to Klipsch Forte 99dB efficiency or Focal Aria at 92dB.  The KT88 can run 6L6, 5881, EL34, KT77, 6550 and KT88 @8-10 W depending on output tube. Pure heaven with the Klipsch. His 300b comes fit with the new production WE 300b for $4,250 and is rated @6W per channel. I was able to pickup in Cary, NC and he treated me to lunch with an audio buddy, tour of his shop the Toyfactory, plus an afternoon of music and career stories.  BTW, he founded Cary Audio, credentials enough! 

One of my 'under-powered' friends has this Art Audio PX25, 6 wpc

https://www.enjoythemusic.com/magazine/equipment/0801/artaudiopx25.htm

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