Quick update: currently demo'ing a couple of preamps from Paul Manos at High Fidelity Services. He has been an absolute pleasure to deal with.
The first one, Audia Flight Strumento n1, wasn't the right match for the sound I'm going after.
The second one, Zanden 3100 tube line stage, is a really serious candidate for purchase. I'm still playing around with it, but so far so good. The music is just pouring out, effortlessly... it has tremendous and natural bass, for a tube pre. The timing, rhythm, timbre... I'm quite smitten at the moment. Absolutely my favorite of the tube preamps I have tried so far. The synergy with rest of system is fantastic... the Rockports have lost a little of that hard edge I was getting before, and I'm finding myself just getting lost in the music.
Any Zanden fans out there? I actually really like the aesthetics of this piece too. A bit different, with the frosted/acrylic front plate... but I listen to much of my music in the dark, and seeing this baby glowing is very pleasing. Really smooth volume control, and sounds fantastic at both soft and really loud levels. I'm liking this one.