Please define the differences between Dolby's
PLIIx - C, PLIIx-M, and PLIIx-X

Which would be the best setting for:
TV, SD & HD broadcast or DISH
Oppo SD-DVD
X-BOx

PLIIx-C: the "C" stands for Cinema, and it's intended for movies and TV (so the TV and OPPO).

PLIIx-M: the "M" stands for Music, and it's intended for producing surround sound from stereo music sources like CD's

PLIIx-G: the "G" stands for Game, so it'd be the recommended choice for the XBox.

The "Cinema" mode is the most commonly used one. When applied to 2-channel sources, it tries to keep maximum separation between the channels. When applied to 5.1-channel sources, it looks for surround information that would normally phantom image behind you and sends those sounds to the rear speakers. Those sounds are also actively cancelled from the side speakers (so those sounds aren't heard from two different directions).

The "Music" mode offers adjustability when used with 2-channel sources. You control the surround processing, choosing exactly how much centre information and surround content you want extracted. When applied to 5.1-channel sources, the Music mode works just like the movie mode, except that rear information is not cancelled from the side speakers. This sacrifices directionality for envelopment, which is more important with music.

The "Game" mode is exactly like the Movie mode, with the lone difference being bass management. The Movie mode generates content above the crossovers, to send to the various speakers. The Game mode generates full range channels and sends the content above the crossover to the various speakers. It then takes what's left of the full range channels and sends that info the the subwoofer. If you like an extra bass kick, use the Game mode when watching 2-channel movies or TV.

OH Yeah !
Great description & info Sanjay
Thanks for sharing...and clearing up all the different modes...much appreciated...