OP: please see this old thread from about 7 years ago in which I asked a very similar questions. Perhaps there will be some value in it for you:
https://forum.audiogon.com/discussions/setting-up-dual-subwoofers-to-a-two-channel-amp
https://forum.audiogon.com/discussions/setting-up-dual-subwoofers-to-a-two-channel-amp