Unless you do a lot of music listening in 5.1 you won't notice much. There is not that much critical info being sent to the surrounds where your ear will pick up a huge difference. With surrounds you get a little leeway with non-matching speakers. The biggest thing you will notice is trying to get the levels to match as the horns are pretty efficient.

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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose