Yeah, the Sony site isn't the best for details. Here is what it says under the "Specifications" tab for the BDP-S550:
Audio Features
* Dolby® : Yes & Dolby® TrueHD bitstream out over HDMI™ (V1.3)
* Dolby® Digital plus Decoding : Yes
* Dolby® TrueHD Decoding : Yes
* dts® Decoding : Yes
* dts® Output : Yes
* dts®-HD Decoding : Yes
* LPCM : Yes (multi channel decoder): Yes (HDMI™ bitstream out)
* Dolby® True HD bitstream output : Yes
* dts® HD bitstream output : Yes
However, on page 66 of the user manual (at least the .PDF from their web site), it shows the following:
