I have a Mac Pro Late 2009, and just got some Logitech Z506 speakers (http://www.logitech.com/en-us/speakers-audio/home-pc-speakers/devices/7191). There pretty sweet but I don't think I'm getting true 5.1 surround sound because I'm using only the green cable which plugs into the analog out in the back of the MP. Is there someway of using the black and orange cables too? Can someone point me towards a converter or something? Also is there a way to use the optical out? I've noticed there isn't much for sound cards when it comes to the MP.