Have you thought about Heidenau's?
http://www.moto-amore.com/heidenau/new/productsnew_b.htmlI have sworn (amongst many other loyal Heidenau fans), these are the best out there, I put them on my buddy, double the life, and great grip. Available in 'S' speed rating without worry.
PROPERGerman manufacturer, not just a German name, I just (on Friday) put a new K66 on the rear of my x500, so to early for any reviews, but they are awesome, and made for wet conditions.......