If you are considering making the move to a surround mixing setup, there are some acoustic issues that must be addressed. Acoustically treating a control room to yield an accurate surround-mixing environment can be quite different from treating a “typical” control room in which stereo monitoring is performed.
A 5.1 channel surround mixing environment requires that absorption be used to yield early reflection control at the room boundaries near all five surround loudspeakers, not just the front two used in a stereo mixing environment. Whereas 5.1 channel listening and mixing environments allow you to hear much greater detail in the program material, especially with regard to reverberation and other ambience, diffusion is not usually appropriate in these environments because it would make you think there was more ambience on your tracks than there really was and negate much of the painstaking work that went into the surround mix. Obviously this is not desirable. [Note that if you are setting up a room for 5.1 playback only (no mixing), you might benefit from diffusion at the rear of the room if you are using dipole surrounds.]
For the mixing environment, we advise room surface absorption all around (including the ceiling) a reflective floor and we also encourage you to strongly consider beefing up the absorption materials (i.e. 3″ or 4″ Auralex Studiofoam Wedges instead of 2″) used so that even, broadband absorption is achieved. Symmetry is very important when implementing the acoustic treatments in a room in which accurate 5.1 mixing or listening is to be performed. Extra low frequency absorption is advised due to the LFE (the “.1″) channel’s extreme bass output capabilities.