Have you ever stayed at the Iberostar properties? The newer one (Maya, I think) has several specialty restaurants to choose from so you could have a fromal dinner every night. I thought the food was comparable to the RIUs though, so you might not like it. IMO, AI food is not as good as eating in restaurants. There are many upscale restaurants in Playa to choose from where you could dress more formally.
As for hotels, are you looking for 5*? Did you check if you can stay at Royal Porto Real without doing the All inclusive? I think that's an upscale hotel, and best of all, it's right downtown!