Lkdog,
I didn't mean to confuse you.....
The key here is 'properly set up' meaning that you have, for example, minimized your reflection points and are hearing the direct sounds from the speakers from the sweet spot. When you have set up your speakers and have not delt with the reflection points sufficiently then speakers which have a fairly flat output well off axis will in fact be bouncing in phase sounds off the walls, ceilings, floor, etc, and create are larger BUT more diffuse sound stage. That is exactly why so many folks pay such strict attention to room acoustic's and treatment, or some folks like omni's.
Another thing I have found is that when folks say they are hearing sound outside of the speakers, and its not out of phase sound from the recording itself, they are referring to sounds that are appearing well beyond the plane of the speakers (behind the speakers) but when you draw a line from the listener to the speaker and beyond to the wall, the sound still appears within the triangulated area.
It is inherrent in the stereo process that in-phase sounds heard thru speakers which are accurate reproducers, typical dynamic point source speakers for example (not omni's etc which are designed to put out a signal in many directions) will only be heard between the two speakers.
However, properly set up speakers, in a well treated room, will at the listening position, allow you to hear all of the recorded information, including out of phase information which is what give the impression of sounds beyond the sides of the speakers. If you don't set up your speakers exactly and treat your room accordingly, you will loose a lot of the very subtle out of phase info on the recording and you will only have sound between the two speakers.
This can easily be played with by using a test disc with in-phase and out of phase sounds. Using one of these disc's when playing out of phase you should not have a centered image at all, and if you are properly set up the sound should sound as if it were coming from all about your room - which, BTW, is a very tough condition to recreate! Its easy to get a vague sound in the part of the room with the speakers, but getting it to sound as if its coming from everywhere equally is a real challenge. And, as you might suspect, the better you can reproduce out of phase info the better your inphase (and overall) sound will become.
FWIW.