A thought:
While anti-polygynists claim men being discontented with one woman is the primary root of their sexual sin, it seems to me to be the opposite.
The biblical principle is that any holy daughter of Sarah is worthy of sexual desire, and that the beauty of any woman, is a jewel of gold, to be honoured and desired, even if the woman is as a swine.
But when a man is discontented with this, and wants his own way, becoming obsessed with only the one particular woman he wants to have, this is the primary root of his sexual sin that I see.
Amnon was a prince, perhaps already married even, but loved and wanted only one woman - which happened to be his sister. David could not be content with anyone but Bath-sheba, so that he committed adultery to have her, and God rebuked him for not satisfying himself with the women God had and would have given him. Jacob loved Rachel only, and God cursed their marriage for this.
Living in righteousness, a man is abundantly satisfied, his cup overflows. What joy would Jacob have had if he had rejoiced with all four women God had given him as Solomon had with his wives?
It is when a man sets his eye on one woman, and stubbornly will accept no other, that he follows his flesh into sin and strife.
So, would discontent with one man be the primary root of a woman's sexual sin? I think this is not the case so much either. This seems to be what is described in Ezekiel in the adultery of God's two wives, however, it makes a point of the unusual nature of their sin.
I may be wrong, but to me it seems an adulteress is usually drawn to betray her lawful husband by being seduced into a "loyalty" to one other man, or she simply desires to spite her lord.
A fornicatress is, I think, usually more attracted in the feeling of subversion, of using her sexuality for the opposite of its purpose, in lording her manipulation over a peasantry of male clients and feasting on conceit, rather than actually desiring sex itself.