Hello from the U.S. First off, sorry I don't speak German, but I would like to share my new project with you guys. I will be using Brembo calipers off a 2005 Touareg on my B5. There are two sizes, 330mm and 350mm rotors. Since my wheels are only 17", I will stay with the smaller size rotors. The mounting holes on the 17z calipers are the exact same as a b5 s4, so I bought the those steering knuckles so I can bolt up the calipers. Companies do make special rotors for this setup, but I will be using Volvo s60r rotors, which are 330mm x 32mm, the same size the Touareg and Porsche Cayenne use. The only problem is the bolt holes are 5x108 not 5x112. So I will need to enlarge the holes slightly to fit, but the center bore of the rotor is perfect. I paid $300 for both of the calipers after being rebuilt, and painted Porsche on them to look cool.
Because the front will be so much larger, I will also upgrade the rear rotors as well to B6/B7 S4 300mm rotors which use a B5 S4 caliper and a special bracket to space them out farther. Here is a picture of what the brake upgrade looks like (someone elses car). Enjoy!