PS3 doesn't output 5.1 to Receiver

[bilbravo]

Hi all. I've been perusing these forums for some answers and have only found that I am now more confused that I was before. This is not due to anyone's inability to explain things, just that I have read some opinions/answers that seem to contradict one another.

Firstly, I have a Sony STR-DG710, an LG 30FZ4D (30" CRT 1080i) and a PS3.

Now, I am in no way an audiophile, videophile, etc. But I do like to get the best I can out of my equipment. The STR-DG710 is a new addition, which came shortly after my PS3 because I needed more than the 1 HDMI my TV set provides and was purchased over the lesser receivers in this Sony line because this was the one that did PCM.

I am running the PS3 with HDMI in to the receiver, audio and video. I have noticed that I never have issues with surround sound from games, but I do have some questions about the BD audio:

1. Bitstream output vs. Linear PCM . I know my receiver will not receive uncompressed PCM, but it does do 48khz PCM (I think--correct me if I'm wrong). When I set the Bitstream output, I get a 5.1 signal--but is it just DTS/DD or is it of a higher quality (I know they have TrueHD, DDTrueHD, blah blah--it all confuses me).

2. When I set it to Linear PCM I only get what my receiver seems to tell me is a stereo signal. I do not get a nice 5.1 signal on my receiver's LCD screen.

Is there any way to get the Linear PCM TO work? Or is Linear PCM specifying that it is "uncompressed"?

I cannot seem to find an answer to this in the PS3's sorry excuse for a manual :-)

Thanks in advance.