Chess is correct and I have demoed Silver FXi surrounds. It is as powerful and has wide dispersion with great clarity and detail. The only issue is the price at more than twice the QS8. I personnaly could not tell the difference when both where only 1 - 1.5 feet above ear level. But if you plan to place the speakers 4-6 above listening level I would tend to reckon the qs8 would do a better job since the drivers are firing down and up rather than the bi-pole di-pole speakers the MA has.
http://monitoraudiousa.com/products/silver/index.html
The only rear surround speaker that I have demoed which seemed relatively close in price to the qs8 with slightly less ummppphhhh is the Warfedale Diamond surrounds. Qs8 detail is a little higher.

Saturn