I hope the kits don't have you add pounds of sugar. If they do, substitute DME (dry malt extract). It'll make your beer much better...probably twice as good.
Also, consider adding some adjunct grains like crystal or chocolate malts. No need to mash and your beer will be much better than straight extract beers. Probably twice as good again.
Sorry for the unsolicited advice, but the subject of sugar use in kits is being discussed in other threads and it's my current mission to spread the word that sugar is not a primary fermentable...just a cheap one