OK, the TX-SR803 is HDMI 1.1, so it can receive 5.1 LPCM. The BD-HP20 will internally decode TrueHD, however it can do nothing with lossless DTS-MA, so you will only hear the 1.5mbit core DTS track.

I just noticed your thread title mentions DD+ (higher bitrate but not lossless Dolby Digital); there arent too many BDs making use of that, most fall back to normal DD or go all the way to some lossless format.