How much space for LCR? It depends on the speakers you choose. For example, if you go with the
Ascend Acoustics Sierra 1 Monitors and
Center (usually available as a package deal through the
system advisor), you'd need about 8 inches on either side + 8 inches either above or below the TV. (Those speakers are 7.5" wide.) Looks like zieg has another idea that would use even less space. For what it's worth, Ascend also has an excellent deal on the Rythmik LV12R subwoofer, if you choose to go with them for your mains.
Judging from the picture you attached in your earlier post, it appears that the primary listening position would be about 15 feet away? If so, then six feet of separation is probably acceptable, but you'll get a better sound stage if you can locate the LR mains on the opposite sides of the door and window. Is that at all possible?