From what I have seen even the cheapest laminate floor fits and feels better with an expensive pad/underlayment. The type I used looks like recycled blue jeans and other fabrics with a built in plastic vapor barrier. »www.quietwalk.com/quietwalk/index.html
I did my living room and my basement with inexpensive laminate and this very good padding, and it feels much nicer than many other houses I have seen with similar flooring without the pad. It quiets the floor, and the padding seems to "take up" the high and low spots.