I've installed a 100 watt Jensen stereo and everything works just fine. The only problem i'm having is with that little button on the center console just past the gear shifter. Maybe its for an amp or something, i'm not sure. But when I press it the speaker in back just groans loudly and its annoying as hell. Is my stereo just too powerful or what?

That little slide switch is the GAIN control. There are 2 voice coils in the rear speakers. You have to disconnect the correct ones from each speaker. Im not sure, but I think that the sound is some sort of feedback from the amp. You can probably just unplug the wiring from the gain switch so that you dont accidentally blow something.

I know about the GAIN control, but what does that other button to its left control? Is it that something in the speakers?

Do you mean that little button with the music note on it? Because thats the ON switch for the gain.....