judsauce
You will get some great advice here, and many of us use tube preamps in front of our tube and solid state amplifiers......the combination can be a beautiful pairing.
I'd recommend reaching out to some of the best tube preamp manufacturers and have a conversation with them; most of them will give freely of their time.....as Lynn has done already. Ralph at Atma-Sphere and Aric Kimball of Aric Audio sometimes post here as Lynn has.
Some of those that I'd recommend are: Bob at Backert Labs (Rhumba Extreme & Rhythm preamps), Lynn Olson/Don Sachs (Raven preamp), Mick at Supratek, (several great preamps), Ralph at Atmosphere (MP-1 and MP-3 preamps), and Aric Kimball at Aric Audio (Motherlode II and XL and Super 6SN7 preamps).
I spoke with each of them before I purchased my Aric Audio Motherlode XL preamp, and they all were very giving of their time.....and you cannot go wrong with any of those preamps