Just putting this here for everyone with a PS3:
Dolby TrueHD, Dolby DTS-HD MA and Dolby Digital Plus audio encoding does not go through optical output, it only passes through HDMI 1.3. Do you have the "fat" PS3 or the slim one? The fat one cannot bitstream dts-MA or TrueHD to a receiver. "Lossless" bitstream can only be done on the slim PS3.
Salesman: Some blu-ray discs have their English track encoded in DTS-HD Master Audio and thus will not pass through optical cables unless the PS3 is in LPCM mode. To get full enjoyment of your BDs, I would upgrade at some point to a AVR with HDMI inputs and can process Dolby TrueHD, etc. Most entry-level ones will do that for ~$400. Pioneer's VSX-921 get good reviews and is on sale right now @ BestBuy for $399.
Here's an PS3 audio chart for anyone that's interested: