if you use that vaux audio matrix make sure you get a balance to unbalenced audio piece like the ART Cleanbox for each zone.

Since your down to 5 zones just use a DBX Zonepro 1260 to do this. it gives you a very flexible system and some really nice integration with RTI. Plus it takes the unbalanced input sources and outputs balanced audio to the amps. the zone pro is an extremely powerful piece and alot of control for each zone! and drivers are already written for RTI