QUOTE(tjh000 @ May 4 2017, 07:26 PM)
First, an update. The 2nd issue seems to have fixed itself. I'm now getting proper volume for the vocals on both 5.1 Dolby Pro Logic (I mistakenly said Dolby Digital in my first post) as well as 2.1 (DPL switched off). When I hooked it up it was playing Life Story from Netflix, which is not encoded in 5.1. That may have been the issue - the encoding of the source material - which cut the vocals out from everything but the subwoofer. David Attenborough sounded like he had Barry White's vocal chords transplanted into him. When I later tried the movie Book of Eli, also off Netflix, and which is encoded in 5.1, everything was great.
To answer your Q yes, there is a 3rd option on the TV, DTS 2:5. Tried it, and it also is giving me all the correct frequencies from each speaker.
HOWEVER, the volume still seems a little soft. Now when I say "soft", it's taking into account all the stuff I've heard about this speaker. It's actually loud enough that I can feel the bass and the room is filled with sound when turned all the way up to 60 (max volume). I just thought it would be louder, is all. I'm just wondering if there is a run in period for new speakers, during which the amp doesn't give full volume. To protect or run in the speakers, maybe?
Either that or I'm getting deaf from all the abuse growing up playing with SPL car audios

Doesn't the S760D have a 'Volume Boost' function? If it works like how it is named, maybe that would work. Have you tried that?
Is the volume consistent? I mean, is the low volume only for dialogues? Also make sure that you're not in some sort of volume reduction mode (like Night Mode). Maybe have a go at turning Dynamic Range Compression on or off (but that feature is only encoded in Dolby Digital IINM).
If switching between all the available codecs and their various settings fail, and you still get low volumes, then it could be a number of things. Your hearing, S760D's design, or faulty receiver/amp section in the unit.