red & white RCA cables, use three wire component cables instead. A better connection. In fact, it is not the speakers that determine digital versus analog, but they are what receive the powered audio signals from the receiver as power source, whether digital or analog.
However, I think the crux of the question is how connect the Oppo disk player & the Onkyo receiver. Note that both the new Onkyo & Oppo can use HDMI (?), so why not buy a cheap HDMI cable from a source such as monoprice.com & use it for "potentially" higher grade connection?
I just recently purchased a onkyo reciever and a oppo(980h) dvd player. I plan on using the 7.1 analog audio to connect to my reciever. My question is can I just use regular rca cables( the red and white ones) to connect it or is there a special 7.1 cables I need......Thanks