Is it possible to buy a decent tube amplifier in the $2000-3000 range?

Rogue Cronus Magnum II if you want integrated, otherwise look for a Stereo 100 if you just want power.

Offer 3k for this:
http://www.usaudiomart.com/details/649194389-dialogue-premium-hp-integrated-amplifier/
this has been listed for awhile.

Theres plenty of positive reviews. The Rogue is good also, but I've seen a few listings used that is the result of going with the PL HP after comparing the two.
Subjective, naturally...YMMV.Rogue made in the USA, blah,blah blah.

If it has to be made in the USA-I'd consider the Rogue and Quicksilver suggestions.

I would not consider a speaker with a 86 dB sensitivity and a load of 6 ohm nominal, 4 ohm minimum as a "very efficient" speaker.

I would think that you would need a powerful tube amp (100-200 wpc) to drive these speakers well, with tubes.
I am not aware of any powerful tube amps costing less than $3K, sorry.

I don't believe that a 40 wpc tube amp will do those speakers justice.
They probably work best with your NuForce amps.

Thank you all for your imput!