Best Integrated amp for under 4k

Ayre is an option...
any others?

Plinius 8200MK2. Not sure what your speakers but it bests with heavy loads such as Thiel or JM-lab. Used one is sold for less than $2k and will give you more room for speakers or even analogue since it has a phono.

Eyal s8-I really haven't heard a lot of amps in that range so the best I can do is recommend the Ayre AX-7-$3K and possibly can be picked up cheaper.
Very well built with excellent binding posts-I think there's photo's in the classifieds on Audiogon.
The sound oozes clarity and detail but also has fantastic bass.
I listen to a wide variety of music and it handles them all well.

actrually im after solid state.
:-)

I am very pleased with my Rogue Tempest Magnum at 42 watts in triode. Matched with my Von Schweikert 100db speakers, the Rogue has more than enough power. It is also very clean looking and the remote is minimal (just volume)and solid. The Rogue owners are very approachable and helpful. And, The Magnum Tempest retails at 2.8K which will save you some cash for other stuff.