if you add caps to the mid base speakers you can increase the bass using the bass controls on the head unit and it won't send too much bass to the mid bass speakers. I'm not talking about adding another amp to the factory speakers. I just want to optimize......

if you add a sub to the factory setup, and look at the factory config, the tweeters are filtered to only supply specific high notes, and the mids are configed to produce certian ranges of sounds, and by adding capacitor to the largest factory speakers you effectively turn them in to mid-bass speakers and let the sub do the heavy bass..... when you filter out the really low end on the mid-bass speakers you can utilize the power in the factory amp to be used more efficiently producing only the sounds the speakers can handle.