Oppo BDP-83 optical out for 2ch stereo from blu-r?

OK, this may be a dumb question, but for the best sound from blu-ray (or dvd) discs should I go with the Oppo 83's analog stereo outs to my preamp, or use it's optical digital output into my outboard dac? Note that I do not have muti-channel capability, my stereo rig is 2 channel only. I am using the Oppo 83 for blu-ray, not as a cd player. For example, a concert on blu-ray disc. Would a HMDI audio de-embedder (hmdi-to-optical digital spdif) converter be something I should look into? Any advice on how to get the best 2 channel sound out of the blu-ray player would be appreciated.
Thanks!