If you wanted to stay with Runflats, have a look at the Bridgestones.
If you want wider and taller, the problem will be that your speedo and odometer will not be accurate.
Here's the link for Bridgestone runflats. They have OEM size or taller or wider.
I wouldn't know what size would suit S-Spokes as I have 16" on mine.
Bridgestone RE050
I have the other Bridgestone runflats on my car. Turanza ER300 RFT and they were much better ride and grip than the original Goodyears.