Here's a few big brake kit options. These may be found cheaper but i dont know many big online shops in the States... only BimmerWorld and Turner Motorsport.
Brembo:
$3495.00 for the 355mm rotor 4 piston FRONT kit
$3795.00 for the 380mm rotor 4 piston FRONT kit
$3695.00 for the 355mm rotor 6 piston FRONT kit
$4,250.00 for the 380mm rotor 6 piston FRONT kit
and
$3195.00 for the 345mm rotor 4 piston REAR kit
http://www.turnermotorsport.com/html...&subcat_id=144
--------------------------------------------------------------------
Stoptech:
$5,790.00 for the Front 355mm 6 piston & Rear 355 4 piston Stoptech Big Brake Kit
$3195 for the 355mm rotor 6 piston FRONT kit
$2695 for the 355mm rotor 4 piston FRONT kit
http://www.turnermotorsport.com/html...ID=83.155.6747
--------------------------------------------------------------------
Again, i'm sorry if these arent the cheapest but i dont know where else to look for them.