Originally Posted by DakarM
you are right and you are wrong
depending on what you are assuming.
the best thing to do is use your stock rotors or brembo blanks and get brake cooling ducts directed at the back of the rotors (probably requires removing or cutting the dust shield)
but that's for someone seriously tracking their car (autox wont make that big of a difference). For street use better brake pads will get you the best brake performance for the buck. this also goes for autox as well.
E30's have the front cooling ducts. I like to think it's Porsche dervived.

h: