Full function or line level only?
You did not specify
I will assume you mean line level only, and so here are three that my friends use or used. (FYI, I use a solid state preamp, the Ayre K-1xe, which is a full function preamp.)
The ARC Ref. 5 is one of my top choices. ($12K new/$7K used) Lots of inputs and it has both single ended and balanced inputs and outputs. Lots of features which are available on the remote control.(Very neutral sounding, without any tube bloom. Could easily be mistaken for a solid state preamp, IMHO.)
(Note: The Ref. 3 is very close to the Ref. 5 sonically, and if bought used, it is a bargain, (@ $5K), IMHO.)
Lamm L2 Reference is another. ($15K new/$7K used) Very, very musical, but a slight bit dark sounding in comparison to the Ref. 5. It does not have a remote, nor is it a true balanced preamp. (Note, the unit itself is actually solid state, but the power supply uses tubes, so I am not sure if this counts for you or not.)
The Conrad Johnson ACT 2, Series 2, ($16K new/$10K used) is also very nice. Lots of inputs (SE only though), and a remote.
My two cents worth anyway.
