Here's the scenario: I have an Imac i7 Denon AVR 1712 Toslink cable. 5.1 speakers I have the Imac running optical out to the optical in on the receiver. I am trying to configure the sound from the audio MIDI setup on the iMAC. When choosing the output it only allows for Stereo (the other options are greyed out and non clickable). Is it up to the receive to decode the surround information or do I need to do it from the Audio MIDI setup and choose the 5.1 setup. Also, is there any way to choose the onscreen setup options for my AVR to show on the Imac screen? Finally, are there any other programs I need, to view and hear 5.1, or can I do it from the installed DVD player on the imac. thanks!