Alright, fired the Smash up this morning. There was some new ringing/jingling in the left channel, but swapping tubes and removing the dampers I bought from Herbie's seemed to have resolved it. In a perfect world I would have been more methodical to understand what the actual cause was but I was excited and had about 20 minutes before my first call.
In any case - the sound out of the fully upgraded Smash is really something. I'm really impressed with the difference the Smashup and SmashQuiet made. It's a little sad it's discontinued! Glad I got one before it went the way of the dodo.