Let me start by saying that the Crossfire has very good brakes to begin with, but I've modified almost everything else so why not the brakes?

In order to run larger diameter rotors, you need different calipers, or a way to move your calipers "out" further to handle the larger diameter. I am not aware of any adapters to let you use the existing calipers with bigger rotors.

The C32AMG brakes I put on the front of my car do several things:
1. larger rotors for more mechanical leverage when you hit the brakes hard.
2. increased rotor size and swept area for better heat disapation.
3. different caliper design -- four pistons (two per side) directly acting on the brake pads plus a very stiff caliper frame design gives you great gripping power
4. larger pads for more braking force

The rears are not as different but do use larger rotors (same size as the stock fronts!) and the rotors are ventilated instead of solid. Pads are also larger and it's a larger two piston set up, one on each side of the rotor. The combination helps maintain the proper braking balance front to rear.

The other big deal is that this setup handles the extreme braking of track events better -- on some tracks my stock brakes would fade after a few laps, and the C32AMG setup does not show this at all. Having driven C32AMG's on the track in the past with no braking issues, I did not anticipate any with the 700 lb lighter Crossfire......

All of this gives greater braking force (my co-pilot complained that she lost her sunglasses and her collarbone hurt from the harness when I hit the brakes hard) and shorter stopping distances (measurements coming soon).

But I run my car at NASA and other track events, and the other big advantage is the better modulation and brake "feel" that lets me control my braking, especially into the corners (this is greatly influenced by the pads used). On the street you usually brake harder as you come to a stop, on the track you hit 'em hard at first and roll off as you end your braking, especially if you are "trailbraking" into a corner.

I've always had big Brembo's on my 914/6 and 911's, my Audi quattro's in the 80's (worked for the rally team) and on my A4 track car here in the states before I got the Xfire. Once you get them, you'll never go back -- the braking feel and results are totally different.