Danman,
If the NAD is compatible with a 4-ohm load (tell him to look at the owner's manual), he could hook up two pairs of 8-ohm speakers in parallel to the one set of speaker outputs. The combined impedance that the amp would "see" would be 4 ohms, and that would be okay IF the NAD will drive 4 ohms without overheating or the protection circuitry shutting it down.
But he has to know the nominal impedance rating of the two sets of speakers he wants to run, and if one set is lower than 8 ohms, he shouldnt't run two pairs from one output.
Regards,
