What spring rates are you running? I've been debating getting some BC coils but I'm unsure of what spring rates to get. I would do it for improved handling and not for lowering it much more than my Eibach springs as I think they offer the perfect ride height & looks.
if you want lowering springs get Tein S-tech, they lower the most and they are really comfortable. I have BC coils now. they aren't the best but the amount you can lower your car is insane. I'm literally scraping the ground everywhere i go.