The best tube preamp is no tubes. If any of you had actually worked on tube electronics when they were the only choice you wouldn't even consider them. In the Navy I worked on a wide range of tube electronics all built to mil-specs. First, a very high failure rate, heat is hell on electronics. Second, extremely difficult to achieve linearity over even the limited audio spectrum in pure class A. That warm sound you hear is the harmonics being rolled off. Feed it a square wave or triangular wave and its lack of linearity becomes obvious. Leading and trailing edges have overshoots and round off. I remember how even multi-thousand dollar Tektronix O'Scopes with extremely wide bandwidth and everything high precision in every circuit could struggle to reproduce these signals.
Everyone here is looking with a microscope for the last tiny bit of performance improvement spending untold sums on wires, connectors, speakers, turntables, etc. and then they introduce all the non-linear components into the mix with tube pre-amps, tube amps, turntables that add wow & flutter and more distortion into their systems.
Granted, some people like certain distortions to their sound but then just acknowledge that you just need to pick the components that introduce the distortion you like and you are not seeking high fidelity. That is fine, if that is your preference, just don't call it high fidelity because it isn't. The military moved away from vacuum tubes as fast as they could because when accuracy and reliability count, tubes don't cut it.
Companies like Fender liked tubes because guitar players liked adding distortion to their playing and tubes provided a more pleasing distortion for musicians that wanted a unique signature to their sound. They even added settings to select your distortion.