I have a Macbook in the living room with my music collection in iTunes that is connected via the audio jack to my home theatre receiver with an optical cable. This works great for my music in my living room. However, now I'd like to add some speakers (airplay or bluetooth?) to my home office in another room in the house. The room is only about 20 feet away so no big distances or thick walls. What is the easiest/cheapest way to do this? How would you do this?