What do you have powering your subwoofers? Also, I don't quite understand the second pair of mains. Are they in the same room or are they for a second zone? Or are they your rear surrounds?

I suppose that if you have seperate subwoofer amps, you could put an ICBM between your player and your receiver for the main, center, and surround channels. The subwoofer channel would go directly from the ICBM to your subwoofer amps. The ICBM should help a bit to keep your crossovers set properly for all SACD and DVD-A material that's coming into your receiver via the 6 analog cables. It would also facilitate setting up your subwoofers as stereo subs.

Hope this helps...