This is a bit of a toughie, I suspect, and on the edge of my own knowledge, so I might have some of the details incorrect. Baaaasically: the way I understand it, Pro-Logic II(x) and its ilk are intended to produce 'decent' surround effects from most basic stereo sound tracks, but also some recordings are 'made' in Pro-Logic II: i.e. they are aware that Pro-Logic receivers are going to be used to decode the audio, and so hide the center and rear surround channel(s) in the left/right audio tracks using clever out-of-phase trickery and so on which Pro-Logic II decoders can understand. Is this correct? Neo:6 is a similar system from DTS, and also seems to give reasonable results when listening to a basic stereo track. But, what happens if you apply Neo:6 to a recording 'made' in Pro-Logic, as above? Will Neo:6 be able to extract the out-of-phase rear channel from the Pro-Logic II matrixed stereo as effectively as Pro-Logic II itself? Will it even try? Can recordings also be made on some kind of special 'Neo:6' soundstage? How do you tell which one to use when you're watching Freeview/Sky/Virgin? Whichever sounds best? Please feel free to critique my understanding of PLII, if it's wrong, as well as answering my question!