Your journey with lower-watt tube amps -- Can a kit be good enough?

@cfarrow Thanks for relating all that. Really interesting.

FWIW, last night I did some listening comparisons comparing the Sun Valley 845 vs. QS Mono 60 w/ KT77 tubes. I used my solid state amp (very neutral) and my Holo Spring DAC. All of my descriptions relate to how things sound in *my* room, of course.

Main impressions: Sun Valley 845's tonality was a bit softer, more detailed, further back in the soundstage, and slightly narrower soundstage (but very good); the bass was weaker, sometimes too weak. It was a bit less snappy in transients but still quite good—not sloppy at all. Instruments and voices had a bit more texture. It was very easy to listen to; never strident or approaching strident.

QS had better transients and dynamics by a bit; it had much better bass, and instruments were more forward in the soundstage. Voices and instruments were detailed but not as much, a bit less warm and intimate.

Overall: hard to say which is better. They were different, though both obviously tube amps. I suspect that a tube amp like the Sun Valley with a bit more grip on the speakers which keeps the intimate/texture/smoothness and improves the bass might beat them both. 

Not sure if any of this translates for folks, but sharing just in case.

 Sun Valley 845 doesn't use an inter-stage transformer between driver and 845 tube.

845 is impossible to drive without IT! You get more driver tube distortions than 845 output stage distortions. You also can't get a good deep and fast bass.

The same I can say about 300B. But 845 is much more difficult to drive than 300B!

For PX25, 2a3, 45 output tube or if kt88/kt66/el34/6L6/6v6 used as SE output in triode mode you can receive a good sound without an inter-stage transformer.

I use a 2016 Dennis Had Firebottle HO (high output, whatever THAT means...max 15 watts pc or something? Likely less with some tubes but, meh...) that sounds astonishingly good with my 99db horns (mid horn damped titanium mid and tweeter drivers Heresy IIIs), and swap that amp with a Pass XA-25 when the mood strikes. 2 REL subs resulting in absolutely no lack of bass, tons of headroom with either amp, and joy in my brain. These amps sound somewhat different but both are so good and similarly mirth inducing that I simply don't need anything else. 

To @wolf_garcia, which output tubes did you land on for your DH Firebottle HO amp?

I'm currently using Gold Lion KT66s, a NOS Amperex 6SN7GTB (looks like a re-branded GE), and a "Tubestore Preferred Series" 274B rectifier. Note I have a drawer full of tubes including more GLs (88s, 77s, 90s, 120s, etc.) and other stuff. The 66s are pretty great, but I'll likely get bored and swap em out at some point...for now they stay.