Also, I had emailed the question to Marantz a while back to get their feedback. This is what they recommended:
Your configuration is possible except you will need an external electronic crossover. When the SC-7S2 is in Bi-amp mode you can use both the Balanced and Unbalanced outputs for each channel. Both outs will send a full range signal to your mono blocks. It will then be up to the speaker to filter the frequencies. If the speakers don't have built in crossovers then you will need an external electronic crossover to filter certain frequencies. At that point, the only option for a subwoofer hookup would be the Record Outs A+B. When the SC-7S2 is in Bi-amp mode both Rec Outs are active. Of course, the subwoofer needs to be an active (powered) sub and have its own internal crossover.
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