NAD 2400 Power Rating x 4 Speaker Hookup?

Does anyone out there know if by hooking up 2 sets of speakers (4 total) to a NAD 2400, is the wattage of power delivered at 100 watts per speaker or 50 watts per speaker. Owners manual does not specify, but it does say 100 watts per channel into 8 ohms.
iirc, that's a 2 channel amp, so the basic answer is 50 each. But I think there's something about the amp also seeing less ohms, and so it's ability to drive the speakers may be reduced. Others who know the technical side will have to chime in, but a 2-channel amp's rating is per channel, even if there are hookups for more than 2 speakers
If you play both sets at the same time, they need to be at least 8 ohm speakers.
If you are planning on playing two sets of 4 ohm speakers at the same time they probably will damage your amp.
And playing both sets of 8 ohm speakers will give you the rated power of a single pair of 4 ohm speakers...
If you are playing only one set at a time, the power rating will remain the same as if only one set was hooked up.