I would look on the Audi forums, a lot of the vw Audi stuff can be swapped. The VR6 calipers and discs may fit, they are good and you can put good pads in there.

The Porsche Boxster stuff may even fit with a bit of work or maybe Porsche 944 turbo....get googling and I bet you will find something.

Often some quality oe discs, new fluid and some uprated pads and brake lines can do wonders, especially if there is any adjustment in the Clevis pin on the foot pedal. A different master cylinder or servo can also do a lot.