what the best way to upgrade the brakes
i believe you must have 16" wheels to use these brakes. i have been told by one of the east coast BMW experts that the best way to improve the brakes on a coupe is to first replace all of the suspension bushings and tighten everything up.
The stock brakes (discs front and rear) are very good so do the full flush and replacement of brake fluid, inspect and refurbish as necessary everything (all calipers, pipes/fittings, MC and clutch cylinders, pads and rotors etc) and that is probably all you will need for street use.
Or go shopping here http://www.iemotorsport.com/bmw/E9-E3-brakes.html