Size wise, if you want to stick with the 16 inch wheels you've got, then you are stuck with replacing with the same size. Many have changed from runflats to improve ride quality, but this may not be an issue for you as you already have generous sidewall depth which probably helps take the edge off the harshness. If you want to stick with the runflats, then there will be better quality tyres than the potenzas, which are relatively old tech. Loads of recommendations on here for various tyre brands - try a search or provide more specific info about what your budget is etc?
