Hi Charles,
I totally lost track of this thread, and its been a while since I last posted. I did make a successful switch over from a passive preamp to the LTA MZ2-S with NOS rolled tubes. Huge difference over the passive. The sound stage opened up considerably and the music just flows naturally now. I could go on and on about the MZ2 as a preamp, but I think there are already many other threads to review this preamp/amp's merits. The synergy is excellent with my Berning Quadrature Z's.
Also, to back track on the La Scala. I learned through experimentation that the USB input was the way to go. I now use HQPlayer to feed the DAC (upsampled), and the difference is huge compared to using a transport at 44.1kHz. No more complaints about the La Scala. It is a keeper. No more lacking for detail, rolled off top, or forward sounding. Everything I said in my post from a while back, I now take back. This DAC is a totally different animal with USB vs SPDIF. I sold my transport and have moved to computer based audio now.