Why do I need a car amplifier for my speakers?

Often the amplifier is part of /built-in to the radio.
People often want a new amplifier/stereo system to output more power than the existing stereo system does.
i.e. the output of the stock radio system is 10-25Watt when buys their own, they can get one that pumps 100Watt per speaker.

You can spend a fortune on speakers, but the amp is what makes them thump.
The signal coming off the head is not leveled to support the high-end speakers, and you'll loose signal quality and volume.
The amp levels off the EQ from the head unit and adds volume and definition to the signal.

Stock amps are usually under the dash somewhere, by the head unit.
Aftermarkets are usually in the back by the sub.

Risky move putting high end audio equipment into a car you can break into with a box cutter.

If your speakers are damaged (rattling, blown) you can just replace them as you intend.  Make sure you get the correct dimensions and I believe you should be fine.
The issue could be that the noise/reason you want them replaced is not an issue with the speakers, but with the stereo.

Ok, that explains that. It has an aftermarket radio. Wonder if he even used the stock amp. When/ if I find it.

Yes the jeep is open range for thieves. I want to replace the speakers  where they currently exist and not be showy to entice

Yes, my sub woofer is out. The others work. Somebody put in a newer radio. I'll replace the speakers with what I hope is close to the same of what I have.

I guess I won't bother with an amp if it plays through my radio?

Here's my radio
image.jpg

The radio I have is 50watt? Or the suggestion?

What I am looking at:
http://www.crutchfield.com/Responsive/Product/CompareTo.aspx?compareItems=01|500SPS510&compareItems=01|575P152&g=400

The amp is built-into your kenwood. you likely have a 4x6. I believe only custom stereo systems actually would have a separate Amplifier often depending on size under the seat/dash if room is available  or close to where the huge Subwoofer is in the rear since one has to run new wires from the amplifier to the speakers it drives.

Are you looking to just replace the sub woofer/speaker affected?
Did the sub woofer suddenly stopped working, double check on the kenwood the rear output selections were not switched. (switch PRE does it show rear or SUB-W)?

I wanted to replace all the speakers so I would know they all were new. They all play except the sub woofer in the center where the hand brake is and if scratchy and quite.

Have not bought the speakers but purchasing now. It's an old jeep with several previous owners so starting over with a few new items should be good.
Thanks for all the help.
I'll post again for help with the install I'm sure!