I think part of my problem is I had my head where the sun doesn't shine (at least not much anymore). It turns out the issue was a 3C24 tube in my amplifier. I have no idea why I was so convinced I thought it was the preamplifier, but that's what it turned out to be.
So, things are going swimmingly at the moment, which is how I like it. In my current condition, just keeping things dusted and adjusted is about all I'm able to for the most part.
I saved the best for last, though, the music has never sounded better.
Best regards,
Dan