Greetings,
I found that my former 6.1 system created an almost un-natural rear sound in that it almost felt like a phantom effect that was hard to tell if it was coming from the front or the rear. I think someone else posted a similar observation somewhere several months ago but I can't recall. It is kind of hard to describe, but definately was noticeable. I heard an immediate improvement when I went to 7.1 with a Yamaha 5790, m60, vp 150, qs8 and Hsu STF-3 using Pro Logic IIx.
b.