Object of My Affection. Definite poly potential in that one.
Now I'm not sure which relationship it would have fit in or if they should have just added another relationship, but Love Actually could have added that aspect. They do include what appears to be an orgy at one point and they do touch on infidelity and the friend being in love with his best friend's girl...but nothing more than that.
Life is about the journey and not the destination,
so what better way to know life
than to wander all the roads and paths set before you.