I have a Yamaha receiver, but on mine I have to set the input to "Auto" or "Digital" to get sound with my TOSLINK cable from my DVD player. There is also a "Analog" setting for standard RCA patch cables. If your receiver is set to analog (or something to that effect on the Denon) you won't get sound with a TOSLINK or Digital Coax. And, you only need one TOSLINK or Digital Coax for each component.
Shinerman