[3liter1]

I have the TC Kline setup, and I believe the price is actually a few hundred lower than on the link (Koni now makes a 128 specific damper that required less modification) Call TC Kline.
I am very happy with them, though I am starting to wonder if I will need new subframe bushings (expensive) as strongly recommended in the TC Kline posted article (search). Also , there is some clunking over road holes, presumably from the Vorschlag camber plates, though some here have posted that it is the koni's making that sound. Decide if you think you need camber plates or not.
Finally, I would described the ride not as harsh, but very "wired", and mine are set almost at the softest setting. That said, steering feedback and performance on turns is incredible. Too bad BMW does not build this into their sport packages (but then they might sell fewer Ms)