With two hours and no checked bags you should be fine. Just keep an eye out for AA schedule changes that could reduce your layover time (common at PHL), or flat out cancellation of your return flight because of a number of reasons (also has occurred at PHL). Just curious why you just don't fly Jet Blue from Logan to SXM directly. They still have that flight, don't they? If the savings was that significant I suppose I could understand why you would want to deal with a connecting flight. But, if the savings are less than $100 each way I would choose a direct flight every time.