Well, I'd recommend Austinhomebrew, and Northern Brewer for sure. I've done some of their kits and have been very pleased. I've never done one of their APAs, but I had done plenty of their other kits before I went AG.
Or, you could find your own recipe and order the ingredients. I'm sure we have several in the recipe database. The nice thing about buying one of these kits from a reputable company is you get excellent instructions along with all the ingredients and everything you need (like priming sugar, a grain bag, etc) that you might forget otherwise.