Markphd, I find your answer simplistic since the inventors of stereo (which means solid) found that it required a minimum of three channels across the front but, due to the technical limitations of the media of the time, only two were used in the commercial applications. There is a need for a good center channel, even if one sits in the "sweet spot," because the center signal information limits the spatial resolution to the sides.
This is not to say that 2channel stereo cannot be impressive and satisfying.
Kal
This is not to say that 2channel stereo cannot be impressive and satisfying.
Kal