I've got an intel mac pro with logitech z5500 5.1 surround speakers (another surround sound question. Yay!). I've got the speakers hooked into my mac using an optical cable. When I go into the midi audio panel and select the configure speakers button, the only thing that is enabled is Stereo. the 5.1 option is grayed out. All I want is to have some surround sound in World of Warcraft like I used to have on my pc using the same speakers. Any ideas why the 5.1 option would be disabled?