Lots of threads on this. Google search 'site:rs6.com brake pads' or similar keywords.

http://www.rs6.com/showthread.php/26...-Hawk-thoughts

Zimmermann rotors are your best bet but can be hard to source. Check with user G2 on here; he might have a nice deal. I got my fronts from him and found my rears at https://www.europaparts.com.

Pads can be replaced separately if rotor is in good shape.