Greetings and welcome to the forum from south-central Texas!
Different breeders specialize in producing different types of Dobes. Depending on what you want to do with your Dobe once you have him/her will help us in deciding which breeders to recommend.
What are your plans and goals for your Dobe? Conformation showing? Agility? Obedience? Tracking? Search and rescue? Personal protection? SchutzHund? Ring Sport? Therapy Dog?
Of the three states you mentioned, I can suggest the following breeders you may wish to research:
VT: Welcome to Rebholzer Dobermans
MA: Kettle Cove Dobermans & Whippets
MA: Manarjj Dobermans and Boston Terriers
There may be others that other DT members know and can recommend.
However, you'll have better results if you know what you want your Dobe to be able to do before you contact the breeders. That way you won't waste your time and theirs by inquiring about Dobes that ultimately won't suit you or your lifestyle.
If you are looking for a Dobe as a family companion, I recommend you check out the wonderful family companions available for adoption from Doberman Rescue Unlimited
, in Sandown, NH.
Best wishes for a successful DoberSearch.