im a little confused by the way this was worded. Im going to assume you are wanting to run your amps bridged in mono to get more power on a 4 ohm or 2 ohm load. This would require two amps to do your highs and lows on your left and 2 amps to do your highs and lows on the right. To cascade and change the amp parameters you will need acp workbench. And then you can connect them together through the spdif. Frank explained this to me awhile back. Havent done it yet though. Here is Franks explanation:
Great idea for digital crossover 
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“For hardware connection, you can configure SPDIF of AMP2.1 as output, and connect GND and SPDIF to AMP4, and plug out the wifi module of AMP4 as it’s not used anymore, and change input mode to SPDIF IN, so it should work as you expected”.
I was going to use a 2.1 and amp4 but it should be the same if using all mono amps. I ended up doing something different with those amps but makes sense to me. Your second amp will just take input from the spdif out of the first amp. You will just need to use ACP workbench to change the second amps spdif to be and input.