I live in the Boston area, and I have used Jim Fuller of Fuller Sound. He works in/with Goodwin's High End in Waltham. He is truly wonderful in terms of the range of equipment he can competently work on. The costs seem reasonable, too.
Tech HIFi (he actually bought the licensing of that iconic name) in Hanson, MA (South Shore) did an excellent job with my all-tube Scott tuner recently. I think they also do good work.