Set movie to normal Dolby 5.1 (NOT DOLBY TRUE HD) and the HD-A1 player's audio to "bitstream" in the Setup menu.
In the player's Setup for Audio, the "Bitstream" setting can be selected only for:
SPDIF (digital connection), and
In both cases the sound decoding is done by the receiver and not the player. (For HDMI, to have the player do the decoding, the player needs to use PCM)
The 5.1 Multichannel analogs will only transmit in PCM. All audio codecs can be sent via the analogs, DD and DTS plus the new ones DD Plus, DD TrueHD and DTS-HD. Of course CD audio is in PCM by default and the HD-A1 is an extraordinary CD player.
With your present firmware, your DD TrueHD can only be in Stereo format, as you know. On all HD DVD's I believe you can select DD Plus.
As a matter of interest, my first HD-A1 had firmware 1.0 and my present one has 2.0. The PQ is very good in all respects.
As for DD TrueHD:
I was most impressed with the sound quality of the dialogs with "The Perfect Storm". It was as if the actors were in my room and not using an electronic mike of any sort. The surround aspect of DD TrueHD can surprise you, in the same movie one scene below decks while several crew members are talking, one of them comes out from the head and the door closing is so real that I turned my head to see who was there to my left.
For special effects in DD TrueHD, "Batman Begins" gives you a good ride from an audio standpoint.
And "Phantom of The Opera" is offering wonderful music and singing in DD TrueHD. But that movie is one of the first ones in HD DVD and has the lower sound volume... therefore, one needs to increase volume.