Just run the L and R outputs of the marantz into any input on the pre. Choose a high vol level that you can repeat easily like half vol, straight up. Put your test tone on and adjust the L and R relative to the rest of the channels. Now you only have one volume control to deal with (the Marantz) just choose the input on pre set the volume to half and the 2ch system will become transparent. You will operate the Marantz as if the the 2ch system isn't there. Just remember to turn the volume down before changing inputs, a good habit to have regardless.