Welcome!
Your question is a good one (and therefore, not uncommon). I bet if you do a quick search, you might find some good advice on this topic.
That said, your concerns are as valid as your question. Having 4 diffuse Quadpolar speakers might make the rear sound too "unlocalized." That is why many of the members use 2 QS8s and 2 M2s (i.e. two quadpoles, two direct firers).
In my 7.1 set-up, which is far from perfect, having 4 Qs would be a waste. The two direct firing rear surrounds does help to define some of the sound in the back when appropriate.
Good luck!
