Boat diving on Maui is universally expensive. (Nearly twice the cost in Cozumel.) We have stayed at many places on Maui. One plan would be the Kaanapli Beach Hotel. Great location on the beach and walking distance to restaurants, shopping, and they usually have pretty good packages with car rentals. Dive a day or two with Extended Horizons' fast boat across to south Lanai to dive Cathedrals I and II. Then an early morning drive to Kihei (45 mins) and dive with Ed Robinson's Dive Adventures. There is pretty good shore diving from Black Rock close to the hotel. OTOH, you can stay in Kihei, where the dive ops are convenient, but the topside for non-divers is not as good as Kaanapali Beach.