Well, i can give you multiple choices. you can spend upwards of 2 grand, or you could spend about 700$ or 300$ all depends what you want.
with you not knowing much about car audio, how good are you with hand tools etc. if you needed to make a sub box?
right now, i would reccomend if you know how to build a box etc. going over to
http://www.respl.com and looking at the SE selection of subs. get a single 12" woofer, and place a jbl 600.2 amp onto it. Get the amp from
http://www.ikesound.com. then, if you want new speakers also, i would reccomend going over to
http://www.thezeb.com. and then finding a cheap amp to power them. the amp probably would be from
http://www.partsexpress.com and try a phoenix gold amp, that puts out about 75x2watts. then you would need some wiring, and i would run over to
http://www.knuknonceptz.com and pick up a distro block, some 2 ga wire to run from your battery to the back, and then some 4 ga wire to run to the amps, however the phoenix gold amp prolly only needs 8 ga wire, so somewhere you may have to distro the 4 guage into an 8 ga. then you will need some speaker wire, and some rca cables.
or go to your local car audio shop, and shop there, they can be of great help, just come back and let us know what they are trying to sell you.
MIKE