How much braking power should I expect?

[indysteel]

During my recent ride in Tennessee, I felt like I had a lot of trouble braking sufficiently on some dangerous downhills, but I really have no idea how much braking power I should reasonablly expect in the first place. All I know is that my hands starting cramping from the effort of getting my bike to slow down even a smidge. With another ride in Tennessee coming up in September, I'm a little worried. I will encounter some long descents there.

My Bianchi came with Campy Mirage brake calipers and they're one of the few components that I haven't upgraded. I have replaced the brake pads (I think I have Kool Stop pads in their right now), and they've offered some improvement from the stock pads. I keep my rims reasonably clean and my bike shop roughs up my pads periodically to expose some fresh compound. The cables were replaces this spring, although I should probably have my shop check for stretch.

Beyond the bling of a nicer set of brakes (and they wouldn't necessarily have to be Campy), is there a difference in calipers? Is there anything else that I could do to get more out of my current brakes and pads? If new calipers would help the situation, is there a brand/model that anybody can recommend?