subwoofers are a great way to boost your audio in your vehicle and can add a lot of wow factor
there are many types of subs to choose from and many different brands all saying there product is the best
i chose a pair of 12" competition kickers because of how clean they look and how they sound i love theses subs the really do represent kicker very well and since buying them my dad and i installed a kicker audio set up on our boat and i really want to put all kicker brand speakers in my car
you are also going to need an amp in order to power the subs and a sub box to mount the subs
i just bought a simple 1000 watt 2 channel crunch amp and it works really well
last but not least you need audio wires power cable a ground wire (very important) and a rem wire
you will need to hook the audio cables from the subs to the amp
the power cable will connect the amp to the 12v battery in your car
the ground cable needs to bolt on to the metal frame of your car
the rem wire connects to the back of your audio deck in your car
and you will need an auxillery cable (you can purchase at walmart 10ft for 8 bucks) that also connects from your amp to the auxillery ports in your audio deck
make sure you have plenty of wire so you have enough length
you can lift up panels and put it under your carpet in order to hide the wires
make sure you bolt down the subs in the box with wood screws
and bolt the amp in a secure location
and last but not least bolt your box down otherwise it will slide around while driving and could damage your vehicle and equipment
total cost: about $200-$250 unless you purchase different equipment

I pulled out everything from the back of my car, the seats, side panels, everything. I'm going to custom mold new side panels out of carbon fiber and put them in. I will have the subs built into the panels and have everything really smooth. I'll post pics when i get it done.