The other member corrected himself right away (some older players did not support passing hi-res on HDMI). You will definitely get 5.1 24bits/88.2Khz on HDMI from your Oppo player using SACD (I have a Oppo player and SACDs).

As for TV, the signal being broadcast is limited to 1080i (often it is 720p) and you cannot get hi-res audio (they have very limited bandwidth). I even doubt your cable box can output at 1080p. So you can use HDMI for sure, but as you only have 2 HDMI inputs on your receiver (unless I am mistaken), I was suggesting you keep one free for future expansion (HDMI is getting increasing frequent on laptops and computers). Either choice will be good.

I personally like HDMI as it drammatically reduces the number of cables, but my cable TV is on component/optical as it has trouble with copyright protection with my TV (the infamous HDCP).

To recap:
Oppo to receiver: HMDI
Cable Box to receiver HDMI or Component+Optical

You're getting close to heaven!

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