if you want to go really low you run shorter than stock tires. that helps with the rubbing as well, but you have to make up for increased wheel gap with running the coilovers even lower. this means even more reduced travel of the strut and the high potential of bottoming out body parts a lot. however, if you run a little more camber than is typical you can go pretty low and still tuck. the problem with this is a little bit of funny tire wear. the car will handle better, though.
i dont know how low youre really trying to go, but putting the front bumper an inch or two off the ground leaves speed bumps as actual impassible obstacles. either way you go about it youre going to run into serious suspension geometry issues. dave (drunkie) basically has his car set so the tops of the tires are flush with the bottom of the fender and he seems to be doing okay. going another inch lower for him would mean that his lip on the front bumper would more than likely take to the street every so often.