Audio Systems: 1999 Dakota audio system ext cab, infinity logo, dash unit

Question
Greetings,

I am having a problem with the sound of my system. The speakers are buzzing, but not all equally and not sure if it is the player or the speakers. I also cannot find anyone to tell me if the dash unit is just a preamp since the tweeters in the door are Infinity. The dash unit is not marked with an Infinity logo and is only a cassette and AM/FM with 5 EQ bands. There may be an amp in the passenger kick panel that is causing the problem but cannot find a wiring diagram on the Web. I have asked the Dodge dealer and they cannot help me. I have just recently purchased a Sony MP3 din unit and the sound is no better. I plan to install a used Dodge OEM CD unit instead but need to try to figure out where the problem is. Do you have any idea as to the set up of this system? I do not want to pull things apart and just start replacing without some good trouble shooting.

Thank you

Answer
yes there is a factory amplifier some 99 have the amplifiers inside the doors behind the speakers and some late 99 to 2002 have the amplifier under the rear seat looks like this


http://cgi.ebay.com/ebaymotors/01-Dodge-Dakota-Infinity-Amplifier-OEM-Replacemen...

dodge speakers

http://i15.ebayimg.com/01/i/000/8d/7f/23da_1.JPG