Started by swapping to the eibach euro Z4 springs (prefer the .8" even drop) but felt the rears were a bit soft for my liking (characteristics of the cars rear dump under hard acceleration).
The oem rear springs and eibach euro springs were both determined to be 500 ft/lb springs. I swapped to...
Now $199 with free shipping. Cant beat the free shipping and for the money it's a nice subtle addition without having to drill holes.
https://www.ebay.com/itm/254880770368?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=_FaeuxZ-SKW&sssrc=4429486&ssuid=UofBQKtXRxa&var=&widget_ver=artemis&media=COPY
I had 'ClearPlex' installed on mine and it's been great. It was installed about 3 months without any issues. Some complain of distortion but I have zero experience with the ClearPlex product doing such. The cost was much less than the original quote. Paid $450.
Additionally my front windshield...
~ The company who installed mine charged $400 to keep the original leather in one piece so they could be reused. Typically they simply cut them apart to make for an easier install.