I'm a bit south of there in Mass and trekked out to all the LFS within reasonable driving distance a few weeks ago as I look to get back into the hobby (was elsewhere the first time around). In Nashua (Amherst, actually), Aquatic Creations is by far the best. Run by a super nice and knowledgeable couple whose primary business is aquarium installation and maintenance, but also run a store. They stock their customers aquariums directly from their store stock, so do real quarantines on everything. Stock level was low when I was there a few weeks ago as they're redoing their showroom, but I'll be there regularly once I get stuff setup and ready. They also have monthly social events for local reefers. Haven't been to one yet, but will be going.
Jay's Aquatics and Oceans in Glass are nearby in Salem. Seemed better than average, but I wasn't wowed. Further south in Tewksbury is Unique Aquaria, as Pokahpolice mentioned. They seem very good. A little further south in Wilmington is Love the Reef. This place was amazing. I spoke with Archit, one of the owners, who is super knowledgeable and friendly and gave some great advice. Excellent variety of corals and fish that appear very well cared for, and a well maintained store (nothing worse than buckets and junk everywhere!.
Keep in mind this is all based on one visit to each store, so your experience may differ! I do have tons of past experience with stores in the DC area, though, and the couple better ones here compare pretty well with some of the better/best stores down there.