Lee, you need to:
1. connect the left and right channels of your pre/pro to the DSP
2. Connect each output channel of the DSP to the amp. That's 4 channels.
3. Connect the 4 channels of the amp to the LFRs. Two channels go to one 880 and the other two to the other.
One channel is for front and the other for rear.

Make sure you don't cross left and right channels or front and back. Make yourself a diagram and follow it.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated