Can I use them with Blue-Ray, feeding five channels to the processor (pre-amp) or directly to the amp?

In other words, can I buy a Blue-Ray player to get lossless sound (TrueHD or DTS-HD w/out buying a new processor ?

The sound quality should be the same whether the player (PS3 for example) does the internal decoding, of if the player bitstreams the audio codecs to the receiver to decode. It’s the same thing, just two different pathways to the same end result, lossless sound. As an aside, the PS3 cannot bitstream lossless audio. It internally decodes it.

HDMI is the best connection for the PS3. It is the only way to get multichannel lossless audio with the PS3. The required bandwidth is too much for optical.

5.1, 6.1 and 7.1 tracks are entirely up to how the movie studio mixed the film. There are some stellar 7.1 tracks out there. 3:10 To Yuma comes to mind. It’s 7.1 PCM and it sounds fantastic. Though obscure, 6.1 is also available. Movies like Crank and The Descent have 6.1 mixes. However, the vast majority of mixes are 5.1. The magnitude of the soundfield improvement is subjective. My opinion is that it adds to the immersion of the experience, but it’s not essential. Most people would be fine with 5.1.

Is there any difference in sound quality if the PS3 sends the decoded LPCM to a new reciever (Denon 4308 or Onkyo 875) or you send the bitstream info directly to one of these two recievers (i.e., do the recievers do a better job of decoding the audio then the PS3 does)?

Is HDMI the best connection between the PS3 and the reciever or is optical better for the audio signal?

If a Bluray disc indicates it has Lossless audio (PCM) or DTS-HD MA, will it automatically contain 7.1 channels or is it disc/movie specific (i.e., some will be 5.1 others may be 7.1)? If not, how much improvement are we really getting for adding two additional speakers and an expensive reciever?