Best Option In A Tube Preamp $1,800 Or Less - Used

As the title says, I am looking for my best option in a tube preamp with an $1,800.00 price limit. I would be buying used to maximize purchasing power and value.

This will be paired with a First Watt F6 power amplifier. This is a wonderful amp, and with the right dose of tube magic from a pre, should make a great combination. I would appreciate your thoughts on my best potential choices which will add the golden glow of tubes to this scenario. Thanks for any assistance.