not that it matters BUT- AMR, CNR, etc etc are all the same thing- a proprietary connection for network and sound devices. The idea is to make a cheap, simple connector that only the manufacturer can use. A PCI slot has to be regulated, conditioned, and 100% compatible with all PCI cards, while an ACR slot just has to work with 1 or 2 devices that the original manufacturer builds- thus it is a lot cheaper. Further, companies can build ACR cards for much less, because they have complete control over the systems they get installed into- they don't need to build for backwards compatibility.
PCI is a free open standard, but to support it 100% costs money. If your board had a real PCI slot instead of an ACR slot it would've cost more, defeating the purpose of nForce. And, it's slightly cheaper to buy PCI connectors and attach them backwards, compared with AMR risers (those little brown connectors), because PCI connectors are already built by the bucketload while AMRs etc are specialized and built in lower volume.
Sorry for the mini-rant, it's all just semantics anyway isn't it.
More importantly- if the review I just read is correct, your AMR card has an SPDIF connector? That IS an optical connector, just shaped weird. Head to Radio Shack and score some adaptors and it will work with your MD player.
http://www.andrewkilpatrick.org/projects/spdif/ - this page has great info on audio optical in/out connections.
Hope some of this helped...