I replaced the run flats on my SC430 (2003) with Conti Exremes. I now have 35,000 on those tires. The ride has been great, so much better than the OEM tires.
I'm now replacing the Conti's with Michelin Pilot Sports (cost more than the Conti) because Costco does not offer the Conti's.
I got the Conti from Tire Rack and had a local mechanic install them (installation is hard, due to the tire pressure sensors, I guess).