Recommend tube amp for $3.5K used

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.

MV 60 is great ,I own the MV55 and agree the sonics are excellent,BUT member "pdbeher"is asking among others a solid bass which brings the Rogue Zeus into my mind,I was A LUCKY guy and found one in my area this week,well I bought it,I am happy!!!!!!!!!!It will be going into a biamp system with the Rogue M150'S doing mids/highs,while the Zeus will push bass on me Aerial 10T.I am getting there.
George

I own a Vac Renaissance Thirty/Thirty MKIII and the Berning ZH270 and listen to similar music through less efficient Sonus Faber speakers. The Berning is transparent and dynamic, but when it comes to air, soundstage, detail and the emotional impact of the music, my vote goes BIG time to the VAC. As for biamping, I try to keep things as simple as possible... it's easy to lose the magic as things get more complex. Minimize electronics and cabling, maximize speaker positioning and room acoustics. Good luck and have fun!

I'll put in my Happy New Year recommendation for the Aronov Audio LS-960 which sounds like what you requested. Sorry that Santa missed your house with this one.
With its used price down in the $1100 range, it is definitely the "made in USA" bargain among many fine recommendations. Even new, it doesn't require stretching your budget.
I have been a voice in the wilderness on this company for almost as long as my Audiogon membership. I am guessing new buyers are relatively few now that the company sells direct, and the company resolutely refuses to jazz up their website.
Even though my support is kind of on auto-pilot, among other positive attributes, the bass is truly surprisingly wonderful and goes a long way toward showing why this has always been a really fun part of the audio addiction, long before kids started putting sub-woofers in their car trunks.
I need just one more true believer to join my committee to find deserving homes for a deserving amp. Apparently, other Aronov owners are the strong, silent type.

Try a Blue Circle BC28. I had one but sold it because I needed to consolidate into a multichannel for space. I would buy it again if I had the room. They are tough to find used, but if one does pop up, I would tell you to give it a try.