I hear alpine are good, although being into home theater setups myself I can't belive a speaker rate 100-500hz can be called a sub, thats more a mid range driver!
a good clean setup of the battery (optima for best performance)
also a good cap between the car battery and amp helps to eliminate the dimming of headlights when bumping at night. and a good built in cross-over on the amp will get your speakers tuned for tight bass, and a good ported sub in the right location is a must, although a sealed sub works too. sound insolation in the trunk helps but is not mandatory.