ahh you got self leveling. That's more complicated. My car has 4 springs all around so it was easier to change the springs.
I installed H&R sports all around and I couldn't be happier. Lowered 1.5" and got rid of the wheel gap.
http://www.7post.com/forums/showthread.php?t=946848
As for you, I'm not sure I would touch the self leveling. The front should have springs which can easily be switched out, but to lower the back I think you would need to have the dealer do it with their computer and I'm not sure what that will do to your warranty and quality of ride.