OK, DenonLINK is a proprietary interface that transmits the 6/7/8 channel audio over a digital connection from Denon's SACD/DVD-A units to a Denon receiver. I assume they've worked out some sort of deal where this is acceptable. Firewire (IEEE 1394) works the same way. DVD-A and SACD are not DRMed (digital rights management, ie the content producers taking away the consumer's fair use rights), but instead rely on the large amount of data to prevent digital retransmission.
Oppo does not have a DenonLINK output, so you can't use that. Neither does H/K, and I don't think either of them have firewire, either.
Your Oppo won't pass SACD over optical or coax because (theoretically) optical and coax don't have the bandwidth to support that.
Also, don't confuse digital audio with digital video. While HDMI can (theoretically) carry both, DVI is video only. And I believe HDMI carries the digital signal as an extension of the usual SPDIF (coax/optical) range, so it wouldn't be able to transmit SACD/DVD-A either. I could be wrong there.
