Will Dolby Pro Logic IIx hurt the fidelity of true 5.1 surround sound?

No it wont down-convert 5.1. Remember you have 2 variables here: * The player must select the 5.1 track as the default * Your receiver will likely auto-detect whatever the player sends to it and decode it properly. Just check your player to make sure it defaults to 5.1 and you will be fine. Note: The front panel of most receivers tell you what it is currently receiving. And the Menu systems are usually NOT 5.1 so wait for the actual movie to start - the examine the front panel of your receiver to see what is going on. Hope this helps.

No it wont down-convert 5.1. Remember you have 2 variables here: * The player must select the 5.1 track as the default * Your receiver will likely auto-detect whatever the player sends to it and decode it properly. Just check your player to make sure it defaults to 5.1 and you will be fine. Note: The front panel of most receivers tell you what it is currently receiving. And the Menu systems are usually NOT 5.1 so wait for the actual movie to start - the examine the front panel of your receiver to see what is going on. Hope this helps.

If the only connection you have is the red and white stereo connections then you will never have dolby digital 5.1 surround sound. As the name implies, Dolby digital requires a digital connection in order to transmit the 5.1 surround sound audio. That connection can be optical, coaxial or carried on the HDMI cable along with the digital video. If you have both digital audio and analog audio connected to your surround sound system then you would need to select the digital audio input for true surround sound.

I doubt that the nature of the source will be preserved, but studio engineers probably assumed that at least some people would use matrix processing to play back the audio. It's not necessarily a bad thing. Near the end of _Megamind_, Michael Jackson's "Bad" begins playing in stereo, and it seems reasonable that some of us would like to hear it over 5.1 speakers even if the matrix formats are somewhat artificial.

I doubt that the nature of the source will be preserved, but studio engineers probably assumed that at least some people would use matrix processing to play back the audio. It's not necessarily a bad thing. Near the end of _Megamind_, Michael Jackson's "Bad" begins playing in stereo, and it seems reasonable that some of us would like to hear it over 5.1 speakers even if the matrix formats are somewhat artificial.