I'm installing 4 in-ceiling speakers in the 4 corners of my living room, and I'm curious about how to set up the stereo. Should I put both left channels on one side of the room and both right on the other side, or should I alternate them so the two left channels are at opposite corners and two right channels at the other opposite corners?
Are you really committed to putting speakers in the ceiling? That's the very worst place for speakers for many reasons. For proper stereo imaging you need two speakers, pointed at your head, at a height that puts the tweeters at ear level. Anything less will sound like Muzak in a restaurant. See this: