I can assume that you are connecting all your speakers to the XPA-5. Because none of the onboard amplication is being used you can set it to 7 channel normal (default). You could also use 7 channel + front and it would be able to use the front amplifiers for another purpose. The preouts are "hot" all the time so reassigning the internal amps does not matter in your case as you are not using them. Connect your XPA-5 to the LF-C-RF-LS-RS preouts, your speakers to the corresponding channels on the external amp and run YPAO. It will detect the sound output from the speakers and set the rear surround and presence speakers to none.