AutoX/Road race in a dart??

hey autoxcuda, i see your currently running 11.75 front rotor and want to upgrade to 13". is there really that much difference between the two sizes to justify the cost?? i just bought some used viper calipers from ebay and was planning on using the 11.75" rotors. i know they will be better than the stock '75 brakes but now i wonder if i should go bigger.