I am looking into buying a 5.1 system for my macbook (alu late 08). Have had my eye on the logitech z5500, as those seem to have a pretty great reputation. A wireless connection isn't necessary, as I will be using the speakers for music in my office with my laptop. What I am wondering about is the interface. I have only listened to music on this macbook through headphones, and have no idea regarding the quality on a 5.1. Is an external sound card necessary? Do you simply use audio out, or are there USB connections that are used in some systems?