"For this reason a man shall leave his father and mother and be joined to his wife; and they shall become one flesh."
Please note the word of God uses the singular form wife, (not wives). Just because God allowed polygamy in Old Testament, doesn't mean He approved of it.
Also note what Paul says in 1 Corinthians 7:2:
"But because of immoralities, each man is to have his own wife, and each woman to have her own husband."
Please note once again, Paul uses the singular form wife, not wives in this text. Clearly, God's will in one man and one woman in marriage.
The world can do as it pleases, and justify what it wishes with regard to moral law; but you cannot justify polygamy via God's word; which in the end, all men will answer to, and be judged by.
I have studied this topic much more than I expect you have, though I suppose I could be wrong. One man and one woman = one flesh. YES. And one man with another woman = one flesh. YES. See 1 Corinthians 6:16.
Regarding “own” wives and husbands, I encourage you to do a review of the original language and then tell me if your stance is the same. See: http://biblicalpolygyny.com/wiki/index.php?title=Own. Why would Paul use a different word? Why would he use a word that means what “own” means when referring to the wife?