Must be the Behringer HA4600 with its Aux jacks for each channel. Hope yours work well, mine didn't. I had loud hum when I connected the Auxes. Went better as I mounted the device isolated and again better after I removed the chassis ground inside the case. But I didn't use it that way, it was to dangerous - I don't think people want a defibrillator on their ears. Finally I decided that the box is just crap and threw it away ...it has 4 outputs, all driven either by a master input, or each with their own input.
very interesting Matt yes, I'd like your detailed routing for my own education - when you have the time to soare, that is