Interesting thread and worth reading for the variety of opinions. However, my search for a wonder-full, honest to goodness tube preamp ended with the Ultraverve (modded with better caps) followed by lengthy auditioning of vintage 6SN7s. Matches with the very revealing Red Wine Audio amp, I found the sonic character of the single 6SN7 tube to change the character of the pre as dramatically as one could wish. Yes, even to presuppose SS for tubes.
In the end, I settled on three very special tubes: Sylvania metal base, CBS Hytron, and Tungsol black glass 6SN7s. Why three? Because each tube happen to mate perfectly with the sonic character of three different one meter ICs that I already owned: Tungsol with the speed of an Empirical Audio PC Holophonic, Sylvania with the soundstaging of a Ridge Street Audio Reference, and perhaps my favorite, the Hytron with the super quiet(!), midrange spaciousness of the Revelation Audio Labs Paradise. Objectively, and out of context, the Syl MP is perhaps the best of the bunch for frequency extension, but I love the way the Hytron carresses the mids like no other.
Getting back to the UV preamp, the preamp is a machine for letting these tubes shine! If by "tube sound" you mean fully developed mids with a lushness that drips, the Hytron will rip you heart out. So it isn't enough to say you've heard this preamp with stock tubes and label it sterile, accurate, fast, and SS like. Swap tubes, optimize with the right IC, and make sure you have your impedances stacked correctly (actually it is more SS in this regard with benign 50K ohm input imp and a cathode follower that works with a min 10K ohm load).