I have a few questions about the macbook. I have z-5500 speakers and I am wondering if this cable would be all I need. If not, what cable should I get? I have two other questions, can you I get a 3g card for the macbook? Also, which gps system will work best with the macbook? I would of course like to keep both things under $100 dollars (combined) and i am sure that this is a reasonable price.