The EP subs use a brickwall digital high pass filter at 19hz for the 500 and 16hz for the 600 (23hz for the 400 ?) and 100hz digital low pass filters. I believe they are may be introducing a firmware update to increase the low pass to 120hz which will be helpful with blending monitors. When you set the crossover you are relying on the 24db (or in some cases a 12db sloping filter) in the processor which works "normally" as long as its in the band of the subs digital brickwalls.

John