I'm sorry to be the bearer of bad news: this much money spent on AVR and speakers won't help much to see/hear what BD is all about...
Correct. Nothing above 640kbps AC3 or 1536kbps DTS...
It is not a bandwidth problem - optical as transport can handle orders of magnitude more.
The transmitting/receiving parts of the chain are not designed to handle more. It's called standard.
Here is an example how optical can be used to transfer multichannel hi-fi audio
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