Wow! that sounds really strange. I don't know if I have seen a FX processor that has Stereo INPUTS. I would think that a mono input is more pratical for both studio and live applications. (use your aux send #1 to go to the one processor and the #2 to go to the 2nd processor) That makes the most sence to me. A stereo input seems a bit odd. Are you useing it with your keyboard? If so I am a complete idiot when it somes to that. otherwise you would want the mono send and the stereo return. I think that sounds the best. good luck!