Have you tried plugging anything in directly to the NAD amp to ensure the speakers are playing back correctly directly from the amp? You can plug in a iPhone (or similar) with a 1/8" mini to RCA cable and this way you can drive the speakers and adjust volume so you are blowing the speakers out during testing. The NAD has a number of dip switches on the back as well as an attenuator which could be the cause of your headache here. You want to be sure the speakers are wired into the 'SPEAKERS A' terminal on the back of the NAD, that the 12v trigger is set to 'OFF' (I believe), and that the input level knob is set to '0'. I'm NOT sure what the 'FIX'/'VAR' input select dip switch does. Oh, and make sure 'bridge mode' is turned off on the amp. If you hear audio when connected to your iPhone then I would expect you to hear audio from the A/V receiver. I've used the 3313 a number of times, and when I haven't heard audio, it has always been due to the amplifier, not because of the wiring to the amp. You do want to go into your speaker settings and ensure that all the speakers are turned to 'ON' as well, just in case that could be the issue.