transmission line will give you geat bottom end but for a 12" driver it would need to be 7 ft long so no chance,,, bandpass is the way for you in the boot. i would use a sealed box and drive it wiith twice RMS it needs, thats gona give you real fast tight bass which imo is what you need in a car to hear it properly. if you use a ported box it getts all wolly and far too slow etc.