i really need to interject for you gbo1, although its technical adn a definite DIY'er project, you should look into the EBB AND GROW system.
jsut to prepare you, it is a hydro system based on ebb and flow principles, and is more technical than it is exspensive. its pretty much taking a $2000 system and building it for like $300-400.
it uses the same 2gal buckets you are talking about. "urdedpal" was right as far as using 5gal buckets though, nore matter what with this system you will be using a little more than1 foot of height space.