I saw this over the weekend, Three Kids? You Showoffs. As my wife and I contemplate adding to our brood, and coming from a family of three kids, I don't really consider it showing off.
My family is talking about it in part because our children make us happy (even when driving us mad) and at least from my point of view, I would like another shot at having a boy (way too much estrogen in the household--even the dog is a girl). But I wouldn't consider having a third child as showing off our wealth (as if we had some), but rather simply expanding our happiness.