That is a non-HDMI receiver, so I assume you are hooking the audio up via optical. If so, your settings on the audio menu should be the following:
SPDIF: Bitstream HDMI Audio: Downmix PCM
This will give you DTS @ 1.5Mbs for HD audio from HD DVD and regular DD/DTS from SD DVD. The reason you set the HDMI to downmix is because any other setting causes the SPDIF optical to sound muffled. Not intuitive, but it works.
Wow! That's damnedest thing. Is this always or just on specific firmware? This explains why I was not as impressed with the DTS downmixes (I'm optical only) from my A2. I just figured that it was the cost of downmixing TrueHD to DTS. I'm definitely trying this when I get home and watching Batman Begins.
The only ones I know for sure are the A2/A3, but I imagine the other models require it as well. It is cryptically referred to in the manual under the "Notes" section of the "Connect the player to your TV" chapter (pg. 21 in the A2 manual).
As I understand it, you always set the one you aren't using to the lowest quality as it saves some on the processor on the unit. I quess it's because of a limited capacity of said processor. So if you are using the HDMI, set it at auto and the SPDIF at PCM. If you are using the SPDIF, set it at bitstream and the HDMI at PCM downconvert.