I agree with others that Amanjiwo is probably not for a lengthy stay, unless you are a very keen photographer who needs to get special light at Borobudur and also dodge the masses of tourists. Prambanan is definitely worth a trip. Adding another hotel in the Java/Lesser Sundas is indeed rather awkward. Amanwana is fairly specialised and lacks a beach. Next door to Bali is the island of Lombok. I went there several years ago and thought it looked like Bali several years before that. I'm sure it is fairly well develop nowadays but it's worth considering. The scenery is dramatic and there is good snorkelling on the Gili islands off the west coast and even better snorkelling off the Gilis off the east coast if you can organise a trip. There is an Oberoi on the west coast now which looks nice.