A lot of threads on several boards for Litronics. The best deal seem to be from Suncoast Porsche ih Sarasota, FL(
www.suncoastmotorsports.com). They have the Litronic retro-kit for $1095 (list is around $1700) and will accept the $100 PCA coupon (assuming you have one). Ebay acutions come and go with typical prices in the $1000 range.
Everyone seems to feel installation is easy. Only draw back, you will not have the leveling technology (factory install only).
I hope to swap my lights out in the next month or so.