It is like I told the Wife while we were watching the shows:
*"It is easier to be Polyamorous if you are Bisexual"
Granted, it is not necessary, since sex is more of a side affect of being Poly.... just as it is for being married.
Like Marriage, Poly's Infinite Love transcends sex.
If sex is what you are looking for in a partner, I believe you have crossed the Poly line and have fallen into Swinger territory.
*At least mentally