Anyone know if you can mix balanced cables with unbalanced? For example, using balanced for the mains, centre and surround and using the RCA with the back surrounds.

You can mix balanced and unbalanced inputs on the Outlaw amps that support both. This is not a problem as the switching is on a channel by channel basis.

I'm running balanced for my center and surrounds but unbalanced for the mains. There is an electronic equalizer box that is part of the speaker system that must be used for proper sound. This black box (yes, it really is black) has only RCA input/output connections.