A few years back while building up my Axiom speaker system, I managed to find myself with all Axioms across the front and some "brand X" direct radiating speakers as surrounds. While the X models had poly woofers and mylar tweeters VS the aluminum and titanium of the Axioms, the sound didn't come out all that bad!! You could tell the transitions from front to back weren't seamless, but if one didn't dwell upon it....!

.......ok, a Cessna single flying in from the back turned into a DC-3 when it got to the front, but that was an extreme example!