If you want to stay porsche (and above 15"), then go with 16" fuchs or the 7-slot "dish" wheels off of 928's, or 944 club sport wheels. They are all forged, so they are light. Keep in mind that the club sports look 99% like the Design 90, but they have little "impressions" at the end of each spoke.
http://www.wheelenhancement.com/ has a lot of wheels to choose from. Lots of forged aftermarket wheels for porsche, but then they may not fit your car, but it's fun to look
