I cant offer any comment on what springs might be for sale on e-bay, but the stainless ones I got from Motowheels definately feel stiffer than the stock ones. It's not terrible, just noticeable. Stop and go traffic sucks a little more than it used to.
Still not sure why people flock to stainless when Barnett's galvanized springs are available with cups for $15. Plus, I wonder about the metallurgy of stainless as spring material. At least Martin's $29 price is far more reasonable that that other place's offering...
I want titanium clutch springs! don't laugh titanium is a great material for springs. Used for valve springs by many of the top car racers haven't seen them for bikes but my bikes don't use valve springs except some little hair pin things which if I wanted I could do without. I just haven't had the time to do the research but I bet I could find them. I asked Yoyodyne to get some they would be a natural for him he carriers titanium rear shock springs which I have and they not only are a lot lighter by half they will out last the best spring steel.
But, I kept asking him about some powder coated retainers, and finally bought the stainless one after he pormised to send me the powder coated ones when he got them. But, Now he doesn't seem to remember that.