In concept, this will work. A few things come to mind, though. First, the unbalanced and balanced inputs and outputs are not independent (a balanced input is available at the unbalanced output and vice-versa), so you'd only need one connection so the sub and you'd only want one system on at a time. Second (and this is a rather frivolous comment), remember that preset 6 is the bypass mode - you'll not be able to use it for this.