I was fortunate to find a complete set of C32AMG brakes used from a guy on mbworld.org who had had them on his C320 for a couple of thousand miles, and got a good deal --- well under a grand for front & rear calipers, pads, and rotors in great shape. I already had the ss brake lines, so all I did was clean them up, paint 'em red, slap 'em on and bleed the system.
I did change to the EBC Red Stuff pads because I like the greater initial bite they give.....and less dust on the street than the stock pads.

Others have found used front calipers from other MB cars that use the same diameter rotor as the SRT6. Currently there are a set of C32AMB rear calipers only on eBay, but a bit pricey.