I'd suggest starting with the following crossovers, although (as with many things in this hobby) there's nothing sacred about these.

FRONT: 100Hz (based on -2dB point of 87Hz)
CENTER: 120Hz (based on a -2dB point of 110Hz)
SURROUND: 120Hz (based on a -2dB point of 110Hz)
BACK SURROUND: 120Hz (based on a -2dB point of 110Hz)

You could potentially lower these by one setting (to 80Hz and 100Hz), but I suspect you'll get a smoother overall response with these settings.