I have had eibach springs and I liked them quite a bit. Currently, I have a tien ha coilover system, which I absolutely LOVE. Adjustable ride height, adjust spring rate, under/oversteer adjustablity..I love my suspension. I bought them out here in cali for $700 which is a HOOK up and a half. The thing I like best is that I can feel every single bump/divot...everything. I like alot of road input when I drive...

Eibach is good if your just looking to lower your car.

A coilover system like mine is more geared towards racing and dramatically increased suspension performance.

My teggy will out handle an M3....

M3 retail : $47-59 k

My car including mods: $14k (roughly)