I don't know what kind of Jeep you have but I just bought a 2013 JKU (Wrangler Unlimited) and it came with the Alpine upgraded system (130 head unit with the Alpine Sub in the back). The Jeep's sound system just plain sucks. After reading many forums and people telling me just to replace the 6 1/2's with Kickers, I knew this would not help all that much. I didn't want to replace the entire Head Unit but knew I had to spend a little more money to get this system to sound good. I spent $1200 and was it worth it. I can crank my music up to any level without distortion and blowing out the speakers. Here is what I did:
Replaced the two 6 1/2" dash speakers with Hybrid Audio Imagine 161-2 speakers. These speakers have a tweeter in them but the tweeter pulls right out and a plug goes in there. You must take a side piece and under the steering piece off to get to them. It's not hard to do.
Took the two tweeters from the above speakers and replaced the top dash tweeters with them (the front of the tweeter just pops off).
Unscrewed the light bar two 6 1/2 speakers and replaced them with two ARC Audio 6.5 XD1602 speakers.
Replaced the subwoofer in the back with an 8" JL Audio subwoofer (8W1V2).
Put in a Kenwood 5-Chan X700-5 Amplifier under the front passenger seat.
Used Stinger 8 Gauge Pro Complete Wiring Kit (SPK5681R)
Used Stinger 12' 4Chan RCA (S14412)
Used a PAC RCA Line Level Controller (LC1)
Used AAMP Gold RCA Couplers (GRCAS)
PAC 2 Chan Adj LOC with Auto Remote (SOEMT)
PAC 4 Chan Line Output Converter (SOEM4)
It took me about 4 hours to do. If you are not good at this stuff, I'd recommend you hire some audio person to do it for you. This system ROCKS. I now have a separate knob for my sub-woofer. You can't believe the sound it puts out. If you want to have a great system, don't waist your time just putting in Kicker speakers. You have to do it the correct way. Just my take on it.