Best Used Tube Based Preamp $2k Or Under?

@bunkertoy The main differences are that the Aesthetix is more traditional tube like in SQ and is slightly noisier than the VTA 5.5. I've also had the VTA 2.5 and rate it the value preamp in the VTA range. I don't think the upgrade to the 5.5 is really worth it as the 2.5 is a damn good preamp 

I have the ARC ls15 that I bought in 1995 and still using it to this day with not one issue I've done one tube replacement  It does have a remote control I'm thinking of you could fine one used, you can't go wrong 

The Rogue Audio RP-1 sells for less than that new.  The RP-5 probably would be in that range used.  I went from the quite good RP-1 to the RP-7, with which I am very pleased.

+1 on Rogue RP-1

great suggestions here ... just for completeness, Klaus Bunge's group Odyssey Audio has the Candela preamp that fits the budget ... 20 year warranty:

https://odysseyaudio.com/candela-vacuum-tube-line-preamplifier/