Best Tube Int under 4K?

Kora Electronic Concepts Design-30 or the Beard P100 if you can find one.
check out EAR 834. Beautiful, musical and natural
It is a hybrid using tubes on the input side but I think it is hard to beat the aesthetics and sound quality of the Pathos Twin Tower(used 3-3.5k). I own this amp and a couple of much more expensive tube amps and it holds it's own quite well.
Cary sli80.
In my opinion, the best amps at this price point are the Air Tight and Jadis Orchestra Reference. Both offer extension, dynamics, speed, clarity, retrieval of low level information, and refinement that are unmatched by anything else in this class. I feel the reasons for their superiority come down to parts and construction quality. The heart of a tube amp are the transformers. Air Tight and Jadis are head and shoulders over any tube amp in this league. Apart from that, my statement about parts/construction quality extends from the capacitors, to the wiring, to the tube sockets, to the binding posts/inputs, everything. That being said, the infrastructure of both companies is currently almost nonexistent in the US. Leaving service and support questionable. With that caveat, I would say that the Cary SLI80 would be the product of choice today. Sonics are a step back from the two products I listed, however. The reason I ultimately chose the Jadis over the Air Tight for myself was twofold. First, the fact that I could go with so many different types of output tubes(EL34/E34L/6CA7/KT88/6550/KT90), whereas the Air Tight accepts only EL34 type tubes. This gives the ability of the amp to sound almost any way I want it to, by juggling both tube type and brand. The other reason were the tone controls(bass and treble) built into the Jadis. I find these controls useful in quite a few recordings. My fear was that the mere presence of these controls would detract from the sound. Happily, it proved not to be the case. Kudos for Jadis for having the cojones to include these controls in the face of the taboo tone controls have garnered in high end audio. During my travels, I found the next step down from the Cary would be the Manley Stingray, VAC Avatar(best of these three), and VTL IT85. After that would be the Rogue, which is very, very good and the Conrad Johnson CAV50(with the caution that the amp is not the most powerful - would be an issue with a lot of speakers). Followed next by the Golden Tube(out of business, so worse than Air Tight/Jadis) and Jolida line of integrated amps. My opinions on Pathos are that it does not sound like a tube amp, although I do consider it a fine product.
under 4k you must hear the YAKOV ARONOV intergrated, used under $1,500.
Cary SLI50, pure class "A" 30 watts with E34L output tubes sounds like at least double that with an incredible extension at both frequency extremes. Dynamics both macro and micro are excellent coupled with a neutral midrange. If I had to give up all my other more expensive audio toys I wouldn't feel cheated keeping the Cary and my Triad Design system 3 speakers.
Air Tight Atm-2 has been a facter in my music,this amp love's to play music.I pick one up used for $1900 and had Tom Tutay (Air Tight Service) he install soft-start,WBT speaker post,rca jacks, better wire, and some of his updates,grounding, and caps and new vol- pods. Price $2600 so if you look you can find good deals. Doing your home work is the key here. It's takes time to find what work's for you and the music you love. (ATM-2,CD-50,SHEARWATER HOT-RODS,ZEN SHOTGUNS CABLES AND RCA)