Is there a factory amp with the stock system? I have the SXT with the 6-disc changer. I do not have the Boston Accoustics upgraded sound system, or the MyGig. Just the Stereo with 6 disc and 6 speakers.

Do I have a factory amp somewhere, and if so, where?

To my knowledge only the Boston Accoustics package adds an amplifier but that could be incorrect since you have the 6 speaker package. Ususally the amplifier (If you have one) is located under the upper passenger kick panel.