OP, from all quarters I have heard nothing but good things about people going with mild to medium lowering springs and then shaving the front strut guides and using E36 M3 bump stops. I am actually going that route myself soon, with Eibach springs (when my EDC shocks pack it in, I'll go for the full Bilstein B16 EDC coilover kit).
Until then, I have tracked down the relevant part numbers: 31332225377 for the bumpstops and 31302283650 for the front strut guides.
I would suggest contacting
Malek@MRF and reading his thread on the subject
http://www.m3post.com/forums/showthr...ghlight=shaved so you can see if this is something you'd be interested in - it appears to be a cost-effective solution for the want-lowering-springs-without-killing-ride-quality problem.
I have access to a machine shop, so I can shave the guides myself - just asked Malek for some more details RE rubber tubing instead of the rear spring pads since PhotoBucket packed it in. The guides are shaved approx. 8.5 mm on the rubber end BTW.
The idea is that with the shorter E36 bumpstops, and the shaved guides, the suspension travel lost with the lower springs is regained while still having the car sit lower.
Hope this helps!