My 970 was down for a long time and I am trying to reconnect it to my Oppo DV0-980H and am a little confused.

Should I use the 6 RCA multi-channel outputs on the Oppo and connect them to my 970 for the best sound ( even if I am only using 5.1) or just use the digital connection( which I did before)? I want to get the most out of the two components.
Thanks in advance for any help!