I put Eibach springs and Bilstein sport shocks on my 325xi. With everything else left as is, the car now sits at the level of a stock 325i. It dropped about an inch up front and 1.25" in the rear. As for the ride, the car rolls noticably less in the corners, but the ride isn't too stiff to be uncomfortable. I'm very happy with the results. Alternatively, you could just replace the shocks/struts with Bilstein HDs and keep the stock springs. They should be ok for another 80k miles.
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2003 BMW 325xi
2010 BMW M3 Sedan