I have been playing with the position of my rear speakers lately too. I used to have them either side of me (about one foot behind the listeneing position) and at ear level (not ideal but I intend to chnage that shortly). They were facing directly towards the listening position and, even though the effect was impressive, it was too 'in yer face' for my liking.
So...I changed the angle of the rears so they were angled away from me and were facing teh rear walls (there is a space of about six feet behind the listening position), they now seem much more diffuse and not as located as they used to be. The sound is not as 'big' is that makes sense, but it sounds much more realistic than before.....it just looks a bit silly with two speakers facing the centre of the rear wall..lol
------------------
"Why do I do this? Three reasons: the pay is good, the scenery changes, and they let me use explosives."
http://www.ypcc.co.uk