We are also working on booking an adults-only, AI property in the RM region, and from my research so far I have found the Secrets and Excellence resort lines to be the "most for the 4.5 star money", so to speak. I am struggling now with the fact that for the most part, adults-only AIs are rather expensive (ranging between 200-300pp per night!). I have even gone through 2 travel agencies, and have checked with all resorts and their groups bookings sections to see if I can get discounts, but the cheapest numbers are coming in around $220pp per night. With food, alcohol, fruits/juices, room service, and some activities included, this is really not a BAD deal - I had just hoped for something around $150 or so. But I don't think I can let go of the Secrets/Excellence lines -- their resorts both have no problems letting you bring in outside vendors, and their Silver and Gold level wedding packages (the 2 highest) both allow for a cocktail reception and a wedding dinner for up to 20 people...I have yet to find any other resorts that offer such great options in their wedding packages for under or around $3000. If anyone has heard of any, please let me know!
And good luck to you! )