Recommend tube amp for $3.5K used

Almost any monoamp by Quicksilver will fill your requirements. Probably the 120-watt V4s will deafen you quite happily. QSs ALWAYS sound good and are quite reliable.
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You're not asking for the moon. You're asking for a McIntosh!
The new MC275, new or used, would fit the bill. It puts out near 90 watts per channel. Silent as a mouse.
Personally, I prefer the look of the MC275 over the MC2102.

It sounds like you are set on a tube amp, but are you open to solid state? The reason I ask is I was previously using a Cary V12i that offered 50 watts triode and 100 watts ultralinear, which appears to be enough to drive your speakers (if you decide on Cary I might recommend Cary modified AES Six packs as an alternative). I was using the Cary with a Joule Electra LA-100 MkIII and the combination was very synergistic. I recently switched to a TRL D-225 and combined with the Joule Electra I am getting the sound you are after. This is a very transparent fatigue free set-up with excellent imaging, soundstage, and micro/macro dynamics. The bass is to die for and I never realized the amount of roll off on the low end with the Cary amp until I plugged in the D-225. Cost is $4k new with a no-risk trial period.

From a tube perspective, before settling on the D-225, I was looking at both high powered push/pull and SET designs, as well as the flea powered SET amps. Unfortunately my speakers are not as efficient as yours, and like you my preamp and speakers were not going anywhere. The tube amps I was researching which I would recommend are VTL, Berning, and 3-D Audio (custom made SET amps at a very reasonable cost).

Best of luck with your search.

I have owned the Sonata speakers and the CJ MV60 amp. The Sonata speakers are very smooth sounding and easy to drive. They do respond well to more watts however. I pick the CJ MV60 first and the Vac 30/30.

Why CJ first?
- only $1600 used
- 95% of the Vac amp in overall sound
- cost to retube is much lower - those 300B tubes are getting more and more popular and expensive.
- the CJ highs are extended with sparkle which the smooth sounding Sonata will like
- the CJ has more power and the Sonatas like that also they really open up with more power.

The Vac 30/30 is wonderful sounding and it would also be a great choice. Mids cut from the same cloth as the Sonata - so smooth and intimate. Nice synergy with the Sonata.

The CJ gets your there for less money and lower tube costs.

Just my thoughts.

I heard the Sonatas (version III) powered by Audio Valve Challenger 140 monos and this combo was really amazing: rich, vibrant, dynamic and beautifully detailed. The Sonatas can be driven by low powered SETs but they really open up dynamically with more powerful tube amps. The Challengers put out 110W with EL34s and 180W with KT88s.