If you are starting from scratch on a home theater system and can basically control everything from room dimensions to seating positions and loudspeaker placement, then here are a couple of points to keep in mind. 

Please design out inwall speakers.  The further out from the wall the speakers are, the better the soundstage will be and the less need there will be for a center channel speaker.

Scale the musical image to the visual image. If your video image is 50" tall and 2 feet off the ground, make sure your loudspeakers put up a similar sized and placed image. 

Allow for multiple subwoofers placed optimally in the room.  For subs with one in the middle of each wall, is probably going to result in the flattest response and the greatest dynamics.

What are you going to be sitting in? The top of a stuffed chair protruding above your head dramatically reduces the effect of the rear channels. 

If you have wide dispersion speakers in the front, the centre channel will probably be doing more harm than good with the majority of program material. Try the sound system without a centre channel. 

Numero uno in making the home theater room the equal to a great audio room, the video display has to be flat and non-intrusive. Large cabinets for rear projector TVs or cabinets housing the display are acoustic negatives. Keep the front of the room flat and clean. 

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