Jay's Aquatics, in Salem, NH (who currently does only salt) is planning on moving to a new good sized retail space in June, or thereabouts. He says he wants to do 50/50 salt/fresh. That should be a pretty decent place when he opens it.
Up in Plymouth, NH there is a rad shop called Plymouth Pet and Aquarium. I like to go up there when I can, which isn't often because its far away. They have a nice large tank up behind the sales counter with an arowana and other fish in it.