Does anyone get a "pop" on their audio outputs at the moment the choice is made at boot-up?

Yes. The one I built with picker does this as well at bootup, but I haven't tried it from my menu off the quit yet. It's so minor, I haven't even really looked into it. (I guess the pop I had with the Mk 1 on shutdown for the brief time it was installed in dash got me used to things like this :-)