I would go for a used set of bilstein or proflex coilovers. Then you get a kit that is adjustable on compression and rebound, very high quality, and they are not expensive to do service on or change the basic rating on the dampers. I use 3-way adjustable Proflex and i payed 85£ for changing rating on all four with refilling. As said, springs are not so expensive, but more expensive springs usually have more suspensiontravel at the same length as the cheap one. Depends on if you need it. I payed 1500£ for my Proflex, and i,m glad that it,s so easy to fix with them.