I was talking to Lizard King on the way home this evening and he mentioned something about his Denon 3930 that reminded me of this issue (DTS track selected on the disc and NEO:6 the only option for DTS modes).

Check your HDMI audio settings. Is it set to two-channel downmix? If so, try changing to something else (either multichannel LPCM, bitstream, or even no HDMI audio - preferably one of the latter two) and give it another try. I'm afraid that the player might be ignoring the "bitstream" setting because it is downmixing to stereo to satisfy the HDMI output and then using that for all digital audio outputs.