The obsession with coil overs is purely infatuation with racy looking parts and believing they have magical powers.
one thin to realize is that the bushings in the control arms and leaf springs are worn out, shocks will not be the answer, but obviously you need new ones.
KYB are inexpensive but the compression valving is higher and tend to make for a rough ride.
Bilstein have a lot of rebound valving, this would be good with stiffer springs or 100% perfect bushings and springs.
Koni I do not have any data on I have yet to dyno a set.