I would use the tape outputs on the NAD for these connections. The preout connections on the NAD should be volume controlled by the NAD which is not what you want in other zones. You want them with their own volume controls. You can either use a volume control, in the wall, of the room the speakers are in, or you can use a volume control/speaker selector, or you can use a multi-room controller preamp with phone control for volume.
But, it would come out the TAPE 1 OUT into a amplifier which is 4 ohm stable, then out to either a volume control in each room or a local volume control. Then speakers in the rooms. If pricing was right, you could get two amplifiers and hook one up to TAPE 1 OUT and the other to TAPE 2 OUT.
Both of those outputs should provide full line level audio to the amplifier for playback of audio in those other rooms.
A product like this would give you solid amplification for up to three additional rooms of audio for under $150...
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