Whats the application they're being used for?
I had Proflex on my rally car, (Charade GTti) they were great when running it at 100% but anything less and the ride was truly appalling. I sold the car, luckily, before it came time to rebuild them.
I've heard MCA are pretty good but can't personally vouch for that.
I'm happy with my Gaz gold on the Escort, its a road car and I've dropped the front spring rates a couple of times for comfort with no real sacrifice to performance. Mind you it only gets driven briskly on public roads nowadays.
GT Cortina Project "The Ugly Duckling"