Hardware :: Easiest Way To Connect System To Receiver And Speakers

i have a G4 with an m-audio revolution 7.1 sound card. the speakers are cambridge soundworks 510D and the receiver is an old denon avr-1403. i have an spdif cable but the problem is my speakers are "computer" speakers so i cant just go from the digital out on my sound card to the digital in on the receiver and plug my speakers/sub into the receiver. and here's a pic of the back of the sub on the 510D showing the inputs