I think I want a tube preamp

Why do you want a tube preamp? The best preamp is none at all. I think you should seriously think about checking out the Placette linestage (active or passive). What you want is neutrality and transparency, and in my experience nothing matches the Placettes. The active is a bit on the pricey side, but the passive and the volume control (only good if you have a single source component) are bargains!

Ditto on the Minimax. At the price point it is a very good value and what I love as well is the fact it doesn't take up much space.

Patekswiss, I generally find a little bit more body and dynamics preferable to stark transparency that can be just a bit too lean in many cases, just another point of view.

The Minimax, definitely changes the lower part of male and female voices, thinning them out somewhat, taking away the lower body, lessening the sense of presence, and realism. Listening to old Capitol recordings of Dean Martin, then Ella on Verve, is very revealing of this timbral change. Having said that, its not a tremendous flaw for such a low price. But, I try hard not to go completely over the top on a piece just because it is bargain priced. The Mini, with its stock tubes is too forward, with a touch of an emphasis on the 1st and second harmonic, making it too bright for my (again that is my) taste. I compared it directly to the Belles 21A, back and forth, with the NOS tubes in the Mini, and Mullards (in place of the $8.00 GE's) in the Belles, and it was not much of a contest, and clearly, in favor of the Belles. I certainly would say that the Belles for $2500. is as remarkable of a value as I have come across, in the same way the Mini is for $1250. Belles has very little identifiable personality in that price range;it is transparent but not at all thin, offering very good dynamics. The Mini is a value unheard of not that long ago. Listen to both. Of course this is all amp, speaker dependant, for all comparisons as is usual. I was (in favor of Belles) using the 350A Belles, and Von Schweikert VR-4 HSE's. Wow, such a fun way to spend 2 or 3 hours. I love this hobby! As usual, this is IMHO.
Good luck, and good listening.
Larry

By the way; I respectfully disagree with the assessment that 'the best preamp is no preamp', as is stated above. Amps need to be driven. Even the vaunted Berning, with an integrated config, sounds better when used with a great preamp. That doesn't mean that the pre, is invisible, because, depending on the interconnects etc. the sound is definitely changed. But a GOOD preamp, will drive the amp to its best sound. No experienced audiophile, who has made these comparisons would disagree. A few years back, when passives first came into favor (or at least came around with my having noticed), I was personally distressed, because at first, I thought, I was missing something. I thought, I was wrong, because it always seemed to lack weight, and staging, and such, with the passive. Then I started talking to manufacturers of (not electronics, who would maybe have a vested interest in something other than a passive) and they all agreed. In principal, they all said, "Sure, a great preamp always drives the amp better, Everybody knows that." This is a paraphrase, but the meaning is in tact. Systems without active preamps, sound thinner, and have much less dynamic attack and decay. For the record, later I experimented with brand, after brand, and found without exception, active, (read good) preamps always help. Even the Wadia CD player, the most recent attempt at eliminating the need for a preamp; sounds better with a great preamp. This is of course, in my humble (and others) opinion. I am sure you can find others who disagree. Try for yourself.
Good listening,
Larry