Some people have mentioned connecting their source to the Behringer sub ins and passing the sub out signal to the SS so that the SS doesn't have to handle the LF that is already reproduced by the sub. It sounds like a great idea, but the Behringer sub outputs are balanced XLR, while the inputs of the SS are unbalanced 1/4". The big danger is that if you use an XLR to 1/4" cable that wires XLR pin 3 to shield you could damage the SS!
"When connecting an active-balanced output to an unbalanced load, it is necessary to leave the cold output (pin-3) floating. Using an XLR connector, pin-3 should not be connected to anything. If a cable is used with pin-3 tied to pin-1 (shield), the output amplifier could be damaged. This type of connection establishes a low/no impedance path to ground. This means the amplifier will drain current, unimpeded, into ground, which is stressful to the output amplifier." - http://community.avid.com/forums/t/58612.aspx
Is this true? What's the best way to connect them?