depends what your really using your car for. a good amount of companies make decent coils. you got the super duper cheapies that are like under $300 which are raceland coils and can seriously be used for slamming with no remorse. think of your stock suspension and soft feel but with the ability to make it go super low and yes they are NOT dampner adjustable. then there are a bunch of other coils in the middle. megan, D2, Ksport, Cusco, Stance, BC racing. and then you have the big boy stuff. like JIC FlatA2s that are like $2700 for a set. ( might have gone down this is when they first came out a while back). i believe ohlin has a coilover for miatas and so does Zeal but i dont think you plan on spending over $5k in coils.
the reason i said it depends what your planning on doing with the car because each manufacture of coilover has been designed for semething a big different than the next...like they all have different spring rates...