Used amplifier/preamp combo for $2,000-$3,000

For what speakers, in what kind of room, how much volume are you wanting?

Even though I recommended Coda & Classe, which I still do. The combo that Jimmy2615 recommended would be hard to beat. Very neutral and detailed without being overly analytical. Very good bottom, excellent in the midrange through the top end. Solid imaging... Needs good cables.

Excellent combo of the bel canto pre2 with the ARC 100.2 or for a little more money the Cary CAD 200 (though aside from the extra power not sure it's better). Great synergy. 7-10 yrs ago you'd have to shell out 7k for the BC/ARC combo, now about 2,500, and I'd argue as good or better than much of what you'd get today retail for the same 7k or more.

classe DR6 (pre) and classe 25 (amp)

Warm? Smooth? Hard Hitting? Detailed? Power Needed?
I don't know tubes well, but in solid state, You would not go wrong with Coda or Classe. Tons of others, but these are great.