I checked out a new Mesa tech in Austin today - Anthony at the Audio Monk. He recently got "accredited" by Mesa and is on their website.
I took in my TA-15 and discussed how I'm always using an EQ to make up for the stiff mids that I'm fighting, particularly on the clean and light gain stuff. Apparently, the 34k resistor is the culprit. He's gonna put a little toggle switch to go between 100 ohms and 32k, and he's gonna do something to the treble circuit to add more range to it. And he's gonna try to mount the choke to the chassis instead of having it attached to the inside of the cover.
He's a nice guy who is enthusiastic about tone. Hopefully, his work and prices will be as good as my first impression of him.