To be honest I think the KWV3 coilovers are the best option. But, as mentioned above, when you lower the car and put smaller tires on it, its going to be a much rougher ride. Stock will feel like you're riding on clouds as the stock suspension eats up every pot hole with ease. Whereas with coilovers, springs, or bags (I had HP Drivetech top of the lines bags with accuair management on my m6) you're going to feel those bumps no matter what.
I personally think coilovers perform better than bags. I don't care what anyone says about Airrex, Accuair, Corsa Series, Hp drivetech, Broadway static, Airforce, the list goes on and on... bags DO NOT perform like coilovers and are (structurally) more dangerous than coilovers. Period. At least with coilovers you don't have to worry about a bag spontaneously rupturing on the freeway while going 70mph with your girlfriend in the passenger seat scaring the absolute living shit out of both of you. Thats a big perk
