Well Audiolab (in Cambridge) has been mentioned, there is Audio Concepts on Comm. Ave (where Spearit Sound used to be), AudioDave in Belmont, and Goodwins High-End in Waltham.
as to which of them is good ... define your sense of good.
I have heard good things about Audio Concepts but have not yet been, however they are the only one of them who has either picked up the phone or responded to an email. Visit planned for early July.
Goodwins has rarely been open when I tried to visit, and the one time I got through the door I got the 'we don't serve your kind' vibe and left. I'm about to drop 4 figures when I could get something that works for 50 bucks, ass kissing needs to start ASAP. Also they start where Audiio Lab leaves off in price point, they exist exclusively in the diminishing returns segment, which is nice to have but out of my justification. They had a hand in Spearit Sound and I was a little unhappy with my dealings there. Also I don't think they have much headphone gear.
AudioDave has some rave internet reviews, but I have yet to go, and it might be appointment only. Beyond this I have never met anyone who has been to this place.
And Audio Lab. Have yet to have a satisfactory visit there (and being local that means a few in the last few years). The reviews on the utter awkwardness of these guys is spot on. If you want to spend an afternoon talking the comparative merits of vinyl weight for varying periods of Pink Floyd pressings of Dark Side of the Moon then this is probably your place. Getting their attention was hard enough, asking for a demo ... not so easy. But their gear selection tends to be the good value stuff, and the real high end is Macintosh only. Don't recall any heaphone amps, or any DACs, suspect they would look upon me with the scathing of seven devils for asking to hear a DAC. But they do have the better value brands (NAD, Creek, Grado, Tivoli, etc.). Also so I don't come across as completely down on them, they all appear to like good audio, rather than like selling it (which is rare the world over).
Hmmm. Rereading this does sound negative. not meant to be.