Unless you can set different crossover points for the center and surrounds....I would set the crossover no lower than 80mhz. The +/- 3db point on the VP150 is 85hz, and on the QS8 it is 95hz, setting the xover at 80mhz would seem to leave a gap.....that would concern me more for the center than the surrounds. The center carries a lot of special effects info.

-curtis