I'll be the 3rd to confirm the SuperSprox...when I got my new W9 wheel,it came with a really nice black aluminum,but the 500 rips through aluminums fairly quick.So I picked up a matching black steel SuperSprox,I don't have much more than 40hours on it,but there's hardly a mark on it.I'm running a steel Renthal up front,with no problems/complaints at all.
As for the Sunstar...I'm a little surprised you said it's already wearing.When I got my K5,it had a fairly used steel Sunstar on the rear,and I rode a whole season with it,and it never wore anymore than it was when I got it....and I mostly power shift,up and down...and I like to grope the clutch ALOT exiting corners or just pelting the poor unsuspecting punk with boulders too