I obciously need the speakers but what else? Do I need a separate amp for the speakers? And what would you suggest as far as brands and models

This would basically be ideal, but it's discontinued.

Infinity BassLink T Class D powered subwoofer at Crutchfield.com (http://www.crutchfield.com/S-IE6fim8dvKQ/App/Product/Item/Main.aspx?i=108BASSLT)

An integral class-D amplifier powered subwoofer would be ideal.

Bass is non-directional, so only one speaker is needed.

A crossover is generally required, but simple ones are in amplifiers designed for bass.

Usually bass is in both channels, but to use a single sub, you use a dual-voice coil speaker and two amps.

We can come back to this after you do a little research.

They say home and car.

http://www.infiniteelectronix.com/index.asp?PageAction=VIEWPROD&ProdID=1511

In any event, go class D.

You need:
-enclosure
-speakers
-amp
-power wire (to battery - with fuse)
-remote wire(from amp to any 12v powersource that turns on with the keys in)
-speaker wire
-ground wire (amp - chasis)
*if you are hooking the amp up to an aftermarket headunit you will need rca jacks, if you are wiring it into the stock system you will need a LOC (low end converter) stinger makes a decent one for about $20