Okay then, the Output signal doesn't get it's signal from both inputs because it would have to do something to the signal or else you would have constructive/destructive wave interference.

In my reading of your first post, you suggest that the Output line gets its signal from the Back input.
You then describe, in your new method, hooking up output from the empeg to the Front input on the amp which according to your previous statement isn't copied to the Output line. Hence, when the Back input is connected to the Output, no signal would be supplied.

Where does my error lie, in the first point or the second? I don't think it's visualization of the scenario.