Help w/Setup for Pioneer SE-DIR800C

Need some help from the experts here as I am a bit of a newbie.

I just purchased the Pioneer SE-DIR800C wireless headphones. For background, I have an Onkyo TXSR604 receiver setup with my DVD and Xbox running through it (haven't figured out how to run the TV through yet). The goal is to be able to run the wireless headphones for any component.

The instructions for the headphones say to run the digital coaxial out to the headphone transmitter. Problem is the receiver has no audio out that I can see. It does give the option of running an optical cable out, and it does appear the receiver has an optical out. Will that do it? The reason I ask, is the Pioneer instructions assume I will run the headphone transmitter directly out from only one of the sources (e.g., TV) rather than multiple sources running through the receiver and then out to the transmitter.

Thanks in advance.

Mike