While in the subject of 5.1 systems and iMac, let me ask you a question: is it possible to configure the speaker settings from the mac when using optical out?
My room is currently set up so that the 5.1 system focuses around the tv (of course) and my PC (and iMac) are opposite of the tv, so the rear speakers of the 5.1 system are front speakers of the computers and vice versa. Currently I'm using two analog cables that are connected "across" so everything is cool with zero software hassle. The iMac only has one output for speakers so this is not an option.
So, can I use optical line out and configure which speaker is where or do I just have to use the headphone out to get the rear speakers working?