I think the issue may be the direct radiating surrounds in your current HTIB. (And the fact that you may be running them a little too loud.) You're used to hearing everything as a "hard" pan from the back that can be easily localized. This does provide a "wow" factor, but things such as rain or birds singing are not supposed to come from a single spot.
When I first switched from a set of 6x9 surrounds to the QS8's, I was disappointed. They didn't seem to "light up" like the 6x9's did. After a while, I began to realize how much better overall the 8's actually were. (especially with "soft" pans and and ambient sounds.)
