Weight distribution is one of the things that make the m3. If you throw that off by adding different/uneven drop springs you're not really modifying the car you're making it worst. A lot of ppl get coilovers without corner weighing the car, another mistake. These car handle very good on the track on stock suspension. You gotta be really careful when messing with that. Dinan is a great choice if doing just springs. My .02
Grigio Telesto M4, 6MT.