I connect the oppo via HDMI and select which audio mix on the blu-ray, sending it to the Integra. The blu-ray contains different audio mixes, so I am not downmixing but selecting different audio. the output is bitstream for hdmi audio, pcm for sacd via hdmi. That was based on using a oppo 980 HDMI to the Integra 9.8. I preferred the PCM to the DSD so stayed the same when i replaced that oppo with the new BD-83. Then I compare different direct streams using the Integra, direct, stereo, dolby trueHD, so on.
ie another example, "legends of Jazz" blu-ray contains Dolby TrueHD, dolby Digital 5.1 and PCM stereo. Each sounds different, but I prefer the Dolby TrueHD using the oppo. The soundstage sounds larger and each note/instrument is clear and crisp. Easy with the oppo to compare the different audio streams. T