This whole thing is confusing beyond belief... what I've been able to do is play mkv's with DTS 5.1 sound through Media Play, and send optical sound to my HT, and it plays the DTS sound. Dolby Digital is sent out as 2.0 I'm not sure that it is converted to stereo, it appears in my limited testing using a BBC 5.1 test card (Mpeg TS) that the surround channels are just stripped off. Hope I didn't pay for the DLNA functionality, because its useless. Still using my WD Live which I'd hoped to replace. Oh and one more thing, getting the DTS out is a royal pain because the playback will default to PCM 2.0, and so you need to drill through three menus everytime. Now this is Series 6, but I'm betting that the 5 will be similar.