Interesting thread - I've had some of the same thoughts. I've played with thought of adding either a Leben RS-100-U or a Yamamoto CA-04, so I'm looking forward to hearing what's being suggested.
A question:
When you use the preamplifier, I assume you use the pre amp in connection. Does this mean that the signal by-passes the tone and balance controls? Or are these still active?
I wonder if the preamp stage is completely bypassed or still active too.