Before dropping your car I would suggest thinking about speed bumps, mine is dropped 40mm (or so I was told when I was sold the kit) But I struggle to get over speedbumps, and cause a lot of ques behind me while I am getting over them.
I would go for a 40mm drop, I personally think mine is actually a 60mm drop, so I would have thought that 40mm willl be more manageable
Paul