You might have to create a silent center and/or lfe for quad files. My x800 only plays the fronts of truly 4.0 sources.Interesting. I bought mine yesterday and tried some files – and my very own .flac rip of WYWH, which I was pretty sure about ripping correctly from PCM 4.0 off the blu ray, also only played in stereo. I'll investigate this further as soon as I am home from work. FYI I am using the latest UBP-X800 firmware, HDMI 1 goes to my Sony XF85-Flatscreen, HDMI 2 straight to my Marantz SR 6009. DSF-Mch plays fine, as did my rip in Flac off of a Seal Album.
- M.