Well it sounds like there may be some jealousy factors with your freind and this other couple. Maybe not that they want to hookup with this couple, but they envy this couple in that they want to be more outgoing and hook up with couples more easily. In result they may want to be more like this couple that they actually seem to dislike.
I don't know that this is the case, but if it is: My advice to the couple would be to befriend this couple that they seem to dislike, and ride the coat tails sort of. I realize this would require getting over the animosity. However: The thought behind the suggestion, is that as people we naturally tend to become a little like those we hang around with.
Furthermore, it sounds like this agressive couple (and in this case agressive being a good thing obviously) put themselves in situations where more opportunities present themselves, and probably already realize that sitting in the corner or staying at home isn't going to get them very far with other couples. I and the Mrs could probably learn a little from their social skills, as they sound very socially adept.
However, as far as your friend and his or her spouse, they may actually benefit from hanging out with this couple that "swoops up all the new couples in town", just by being in the situations that present more possibilities.
That's my 2 cents....