a good compromise is to have yours rebuilt. they cost less than a new one with a fixed setting like the koni street. with the adjustable kones I had problems that lost oil from the valve on the domes and nobody was able to reconstruct them bilstein instead they seem to be more resistant and above all they use the standard pieces that are easily found to reconstruct them.
the b4 are the same as the standard ones. if you want the car a little more rigid spending as much as a b4 you have to rebuild an original. so you can also decide if you want to shorten the stem or not (recommended if you want to use lower springs).
I've always enjoyed myself with prokit