DeezUU

You already have an amp. It's built into the head unit. Do like JoeMac said and hook up all the mid to high speakers to the head unit and the sub to the amp. An easy way to 'trick' the system into passing the right freqs to the right speakers is to turn the bass down to around 0 (flat) and pump up the mids and highs to taste on the headunit. Then use the amp gain to give you the amount of bass you need. There's no need to drop a ton of money into it. That will work fine and sound decent. If you still need more, THEN go buy another amp. But for the most part... I believe you'll be happy. Remember....it's a Jeep. The more stuff you put in, the more theifs will want to take it out. On top of that is the sensitivity to weather. Electronics don't like water and Jeeps are moisture magnets. You have to find places to 'hide' extra amps and equipment and Jeeps just don't have many good hiding spots.