@rlb61, you're welcome, and sorry if the reply was a little pedantic--didn't realize you were a fellow owner! I too have considered replacement from time to time, but never "got there." And if I did, it would likely be for another BAT tube pre-amp anyway.
If I had more time for listening, and/or a better room, that might happen. But for now, it's difficult for me to find a lot of time (work, three teenagers, house/yard to care for, and boating/skiing from April to Oct). Hope to sell our current home in two years--we bought based on school district and bedrooms so with the last of my kids finishing HS after next year, we can look for something where listening environment is a much higher priority. Maybe then I'd be able to discern some differences, but currently just no point in even trying!
Have you done any/much tube rolling? Any ideas or suggestions on that front?