I just bought a 71k 2006 325Ci and am leaning towards the Dinan setup initially (Koni's and springs) with sway bars/strut brace later. Does anyone know if Dinan has their E46 Koni's custom-valved to their specs? Yeah, I know, I should ask Dinan (or Mike Miller). If they are not custom-valved, I'm pretty sure I can get the Koni's from shox.com or maybe one of the vendors in Roundel for less than what Dinan wants. Springs, I dunno yet. There is also the bare-bones and thrifty option of just reusing the sport pkg springs with Koni's. Comments/suggestions appreciated, thanks.
Perspective from an E30 revamp I would definitely talk to one of the Dinan folks. I am sure that they will tell you that either they custom valve shocks or "mis-apply" (ie use shocks intended for a different application) the ones they use in a Dinan setup. I did a lot of investigating (http://bmwcca.org/forum/showthread.php?t=3603) before I ultimately settled on a Dinan "Stage 1" suspension package for my 1991 318i (E30). Since the interaction between shocks and spring is critical to the performance of the suspension, I decided to cough up the premium to get the Dinan "Stage 1" system. If you buy seperate shocks and springs, you are depending on (albeit excellent) enthusiast testimonials about what works with what. I figured the price premium for the Dinan packaging was worth it (plus I bought during their December sale). FWIW, the 2 rear shocks I got seem to be plain Bilstein's ("mis-applied"?) and the fronts had paper product number stickers that looked custom to Dinan. I suspect the fronts are custom valved. (They really had to scrounge for my E30 shock package: I may have gotten one of the last ones.) FYI, I chose the Dinan/Bilstein option rather than the Dinan/Koni option after some consultation with Mike Miller. Bilsteins are bomb-proof and Konis apparently heat and fade a little more quickly on the track. Minor point, but since these are probably the last shocks my 18 year old car is getting, I thought I'd err on the side of durability. Dinan tried to point me toward the Konis because they liked the way they bottomed out more smoothly/softly than the Bilsteins. They said the Bilsteins bottom with a "clunk". I have not noticed this. Konis were $300 more too. Another little factoid I learned from Dinan is that generally they try to increase suspension travel rather than reduce it (ie lower the car). My 318i stayed at stock height in the back and dropped one inch in the front. Not a whole lot compared to a lot of the other options out there. The following photo is after the suspension install (http://bmwcca.org/gallery/showphoto.php?photo=1425&size=big&cat=&ppuser=147). Maybe this is too much, too simplistic and too off-base of a response for what you were asking: I apologize if it is.
Brian, thanks for your reply as it is useful information to me. I did notice the Koni's in Dinan's product pictures have white labels on them. Their springs for my application only drop the car 1/4 inch which is fine with me. Add an Xi strut top reinforcing plate and the car is back to stock ride height. Apparently non-Xi E46's sometimes mushroom the strut tower top. My only experience with Bilsteins are in Volvos with lowering springs and those were the Bilstein HD's. I have heard that the HD's are for stock springs and the Sport is for lowered cars but we can't get the Sport in the US. The ride is pretty firm with the HD's and lowering springs. Bad pavement is jolting, though. I run the Koni yellow adjustables in my Volvo 240 autocross car. I don't plan to track the 325Ci so I'm making Dinan's Koni/spring package # 1 on my list of shock/spring packages.
My 2 cents - you can't do better than Dinan if you are going to track the car at all - drivers school etc. If you are not going to track the car, look at the KONI FSDs - they work great on my 2005 coupe and made the ride a bit nicer than stock. Jim BMW CCA 144235