Originally Posted by ufokillerz
wow 18ft apart in the back, sounds like a lot more work with my in wall wiring
Then don't do it. Modern surround processing like Dolby PLIIx
runs the rear speakers (and side speakers) in stereo, as do discrete 7.1-channel soundtracks on Blu-ray. In order to hear that stereo separation back there, the rear speakers need to be spread wide apart (especially since our human hearing is not very good behind us).
The 18ft spread was just a suggestion to get your rear speakers 60 degrees apart. If you can't do it, due to wiring or some other limitation, then you can't do it. Just get them as wide apart as the wiring allows.