Preamp Upgrade Time

While I am quite pleased with the sound quality of my system, I have contracted "upgraditis" again.  Over the past five years, I have upgraded my 1990s two-channel system, my new system can be seen in my profile.  My current preamplifier, a Rogue RP-7 version 1, provides very good sound, but I think there is still room for improvement in tonal qualities, imaging, and sound stage.  Sources being sources, I think it is time to look for an improvement in my preamplifier.  At present I am considering several different models: the Rogue RP-9 v2, the Backert Rhumba Extreme 1.4 or Rhythm 1.4, and Audio Research LS28SE.  The Audio Research would be a stretch and requiring saving for a while to get it, but I wonder if it would just be best to make the jump to that level and "be done with it."  About $13K would be the absolute maximum I could go, although I have read of the differences between it and the. Reference 6SE.  I want to stay with tubes, as I think the combination of a tube preamp and solid state power amp gives absolutely superb music reproduction.  While I may be able to listen to the Rogue and Backert models fairly locally, medical reasons prevent travel to audition the Audio Research model.  Finally, are there other tube preamplifiers in this price range that I should consider?