Yyzsantabarbara,
I contacted and heard back from Rory. The only issue regarding my using the HPA4 with my single ended components will be giving up some SNR and that makes sense. As, I won’t be giving up my single ended 300B mono blocks, I need more time to evaluate my options.
Another option that I considered was the Spatial Revelation Raven tube preamp that is fully balanced. I asked Don about using my system with his preamp, and he thought that my single ended amps would not be an optimal use of the system.
Both Rory and Don consider that their preamps are so good, that it would be difficult to find a better preamp anyway. Time is on my side, and will use it to think things through. I’ve been using a 1990 Boulder L3A line stage, and the capacitors were upgraded by Boulder 5 years ago. Single ended inputs with single ended and XLR outs. I’ve been extremely happy with the sound, but I still wonder if a newer line stage in my price range would make more sense?