When I have some time, I am going to use some pink, white noise and tone sweeps to set-up the whole system using a Bruel and Kjaer sound level meter with 1/3 octave band filters, plus some listening tests to finely balance the system to my taste. Will need to balance the system when the car is mobile so have to get a pal to operate some of the stuff. 
Over to you Snoops! 
You want greater than 1/3 octave in my experience as thats an absolute minimum. I also recomend you do it while stationary, theres too many variables when moving. Also varie the mic position by moving it in a figure of 8 configuration at ypur ear levels and set it to continuisly sample and take an average as mics are not as good at collecting the sound as your ears and give false readings from some reflections/absorbed frequencys if only sampled in one place. Tune right side then left side independently so fade left then to the right first, Then adjust together and adjust frequencys to centre the image. Most road noise can be compensated for by boosting a few of the frequencys below 300Hz thats the easy part. Or simple buy an MS-8 and insert it into your system it does 98% of what i can do with a pro 80band plus parametric in 5 weeks constant tuning in about 5 minutes of autotune it makes a huge difference to even an oem system tone and imaging.
