I would contact GC and discuss softer springs with them. You can pick your spring spec based on your needs. Plus you can adjust the ride height to add more suspension travel for more comfort. Far better option than going to H & R springs.
'08 E90 M3 - Alpine White - Sold
'13 E92 M3 - Silverstone II - Sold
'04 E46 M3 - Jet Black - BBS E88, KW Clubsports, Brembo BBK, SuperSprint Exhaust, Recaro
'15 i3 - Laurel Gray - Why would I mod this thing?