To output SACD, you need to use either HDMI or
multichannel analog. In the case of the 981HD paired with a Model 970, you will need to use multichannel analog. I would connect either coaxial or optical for regular CD's and DVD's, and then just use the multichannel analog for SACD's. The setup section of my 981HD review
might be helpful in discussing this, but the 981HD's manual is also quite well written and worth a read in this regard.