amplifier needs

I can think of no reason it would not work if you used reasonably heavy gauge wire, say at least 16 gauge. Try it and check to see if the amp is running cool, if the heat sinks become hot then you have a problem.

Just be certain that the speakers you're using are at least a nominal 8 ohms each. Hooking two per channel will lower the impedance the receiver sees to 4 ohms, and you don't want to go any lower. Other than that- you should be fine.

Wire them in series and you will be fine.

Be aware, though, that wiring them in series, while making life easier for the amplifier, will degrade the sound quality, especially if the two sets of speakers are not identical.

If the two sets of speakers have different impedance vs. frequency curves, the frequency response of each pair of speakers will be altered by the impedance vs. frequency curve of the other speaker.

And even if the two sets are identical, damping factor (affecting the bass) goes down the tubes because the source impedance driving each speaker becomes the amplifier output impedance plus the impedance of the other speaker, rather than just the (very low) amplifier output impedance.

None of that may matter too much, though, if the speakers don't have much bass response anyway, and if sound quality is non-critical in this application.

Regards,
-- Al