I really don't see a benefit from getting M3 springs. They're still not low enough or stiff enough to actually make a significant difference. The thing about springs are that they're reletively inexpensive. I mean, compared to shocks, are even sway bars, you can buy springs anywhere from $200 to $300. I recommend some H&R Sports if you're into a moderate drop (1.5" front and 1" back) and stiff ride or some Eibach Prokits a similar drop with a softer ride.