Aquahut has the best prices hands down but a.) there are NO prices on the tanks so you have to ask a salesperson ( they are not always helpful or consistent and if you dont spend a chunk of change your first time, dont bother asking for help your second time there ) and b.) its hit or miss with their livestock - about 30% of the fish I bought there died in quarantine so I dont know if that negates the discounted prices. Also the fish tend to go quick so if you are looking for something that is sought after by others, you'll be forced to buy it pretty much right out of the bag. Suffolk County Reef has higher prices but their tanks are all marked with prices, they sell frags now, and their live stock tends to be in better condition along with more helpful salespeople. Check them both out if you have a chance.
Edit in response to the next post: I have to agree that Don is fair and helpful, and generally nice to work with. Its a couple of the other guys who work there with whom I ( and quite a few others I know ) have had the bad experience with.