I would not recomend getting coil overs. The 1000's of levels of adjustment gives you lots of oportunity for getting the suspension wrong. Even race teams get it wrong. I did a lot of research into this and came up with the following options
Alpina D3 set up is good making use of SE, Msports and Alpina parts
Hartge does a kit that is softer, but handles much better. They can let you drive a demonstrator to prove it Speak to Birds in Uxbridge
Schnitzer does a kit and again they will have a test car. They guaranteed the kit when i spoke with them and would remove and give a full refund at their cost if i was not happy.Speak to Chris Rositer based in Norfolk
BMW Performance kit has good reviews in the forums
Koni does a magnetic damper kit KSD which gives a great ride and good handling and has good reviews
As for costs the Koni is just dampers at around 600 + Fitting + alignment and would be the cheapest
The alpina would require a bit of research and would be variable depening on which parts you already have.
The Hartge and Schnitzer conversions where around the £1200-£1400 fitted for dampers, springs and fitting and alignment
The BMW Performance kit can be procured on ebay and dealers for around £800 but then requires fitting and alignment.
Out of interest my car is a 330ise and i find it skips at the back, understeers at the front. My feeling is the car has too much rebound damping at the rear and not enough at the front. However i found a very cheap way of improving the skipping. The extra weight of my golf clubs in the dealt with this to some degree. I have yet to change the suspension as it has slipped down the priority list due to having baby's.
Last edited by sohlman; 01-12-2013 at 06:26 AM.
Reason: added bits