I'll take a stab at this ... assuming your have 4 channels of amplification

prepro Left out --> DSP input L
prepro Right out --> DSP input R

DSP Out Rear R --> Amp channel1 in
DSP Out Front R --> Amp channel2 in
DSP Out Rear L --> Amp channel3 in
DSP Out Front L --> Amp channel4 in

Amp channel1 speaker out --> Right 880 Rear
Amp channel2 speaker out --> Right 880 Front
Amp channel3 speaker out --> Left 880 Rear
Amp channel4 speaker out --> Left 880 Front

Have fun