I have to mention a couple more worthwhile places:
Julio's Liquors in Westborough
The very high end stuff is kinda rare, but the selection is large. Last time I was there they had 7 or 8 Plantations, for example.
Koyal's Liquors in West Warwicke, RI
Good selection with a few notable high-end rum (Pyrat 1623, Clement Homere & XO). And their inventory is online.
http://www.oxfordwineroom.com/wineon...etype=85&B1=Go
Well knock me down. They're listing Matusalem Gran Reserva for $22. Bargain!