What to do about the m3 suspension set-up?
First up: BMW continues to make the standard suspension too soft, set-up with too much unsprung weight that creates an ugly wheel gap and too high a center of gravity. I think the EDC will help "tighten up" the car compared to an e46 m3 but still has about 2-3 inch of gap in the front (terrible).
What to do? I see three options:
1) Aftermarket coilover: Do not order EDC or the technology package (EDC part of) if you do this.
PROS: You will be able to dial in the height and damping (ex PSS9 or K2) to your liking. I have a Pss9 on my e46 m3 and it is amazing. Totally transformed the cars' handing and ride height looks a lot better.
CONS: BMW suspension warranty void, resale value?, No Mdrive option (tech pack).
COST: ~$3000 for kit and installation/corner balance. But you save ~$1000 with no EDC so net $2000 out of pocket.
2) Order EDC + new springs: If the cars height appears ok to you then I would definitely go this route. Although EDC will never match a coliover it should be a step-up from stock.
PROS: Firmer suspension option, no warranty issues.
CONS: No height adjustment. Limited aftermarket options. Springs may not get the exact height your looking for. Jury is out on the long term impact of changing the springs.
COST: ~$2000 EDC + new springs/installation. ~$4000 additional to potentially replace shocks/EDC sensors over the long term.
3) Stock suspension (NO EDC): Just change springs.
PROS: Firmer suspension, lower height.
CONS: BMW suspension warranty void, resale value?, May not get the exact height your looking for. No damping adjustment. Jury is out on the long term impact of changing the springs.
COST: ~$1000 spring/installation. ~$2000 additional to potentially replace shocks over the long term.
As for me I'm going with coilover but if you don't go coilover I think EDC is a must have. The lack of the Mdrive (in tech pack) will suck but the the car needs to be lowered for the couple reasons already stated. Just adding new springs is a half-assed idea (you spent $60k so set it up right).
There you have it. Good luck......