It really depends. If you are looking for better handling from stock, Eibach springs are very good (I have pro-kit springs on my car). Most coil-overs only offer hieght adjustment as the option over just swapping springs.

In my opinion unless you go to KW V2 or V3 or Bilstein. There is no reason for going to coilovers over springs. The higher end coil-overs allow you to adjust hieght, dampening, and rebound which allows you to dial in the car to the nth degree.