Since you already have ZCP, the only thing I would do is to get a high-end coil over... at least KW CS or equivalent. Don't bother with the lower end set ups. The M3's suspension, while somewhat soft, is very competent and predictable, and you haven't experienced its true potential until you've taken it onto the track.
2011 E92 M3 DCT
1991 Spec Miata
2008 E92 M3 DCT - KW Competition 2-way / Brembo 365 BBK / OMP ARS racing seats / rear seats delete / GT4 aero / AiM EVO4 data logger / SmartyCam racing camera
2008 E92 M3 6MT
2008 E92 335xi