There's no real "KIT" so to speak. Usually people just slap some Lowering springs in their car, and call it a day.
Now if you wanna go lower than that, you can buy or build your own coilovers. Or Build/Buy airbags, and get a decent management system for the bags.
I for one, say the best thing for these car's is a set of DIY coils. There's a few good threads on here for those, and i'll be adding my own shortly.