I can only speak to the AD's in Boston, so not sure if that helps. Although 2 of the AD's have locations in Natick, which is the closest you'll get to central MA.
EB Horn in Downtown Crossing carries a VERY small inventory, and I've never found their prices to be that great.
Tourneau has a couple of locations, including Natick, but I've only been to the one at Copley. They have a nice selection, but again, their prices seem high. To me, it seems like the volume of watches that they move can't offset the high cost of their Copley location (or the the other high end malls that they occupy). I also wasn't a fan of the salesperson that I spoke with. Even though I was wearing a Breitling, seemed very disinterested and had a "take it or leave it" attitude. Obviously, that could have just been one person.
I've purchased 2 Breitlings (and an assortment of other jewelry) from Long's in downtown Boston. Their prices are very competitive, and I have always enjoyed working with the people there. My wife bought my first Breitling from Long's in Braintree, and had a very similar experience. Seems like you can very easily get a 15% discount off retail, and 20% if you stick to your guns a little. For my recent purchase, I was able to do better, but again, they consider me a regular. That being said, it never hurts to ask.
On another note, I must say that the inventory at Long's is lacking, and I've been a little frustrated with the waiting period for my recent purchase. You can read more here:
viewtopic.php?f=7&t=9146Hope this helps.