All depends on three factor as I see it.
1. How much money you want to spend?
2. How low you want your ride?
3. What sort of a ride do you want as in comfort?
If you want to drop it by 30-60mm, with still a smooth rider - then I've found that Weltic kits are the best - but can be a little more expensive than most, you can get lowered springs from 50-200 depending on make and other lowered spring kits from 150-350.
If you want to drop the car more than 60+ then coilovers are the way to go - there are many models to go for, but FK Suspension coilovers seem to be the fav of the moment - if you can afford it go for FK Konigsport coilovers - as they are fully height and damping adjusted..ÂÂÂ

- you can then change wheels and height and ride comfort any time you likeÂÂÂ

Have a look at all the different models FK provide as there are a few.
Other coilover models that are good are K&W - very expensive, AVO, KONI. (there are loads other - just can't think at mo...)
Note when you start going really low on mk1's depending on your wheel size, you may need to start cutting the arch's or rolling them.