Stereo suggestions, thoughts, ideas?

I'm sure there is other forums I could ask this on, but you guys won't beat me down because I don't know the answers or if it is a stupid idea. Not sure if this should go here or electrical.
I have an underdash Panasonic 8-track with a fm radio cartridge in my Dart convertible. I would like to put an amp on it to boost the volume a little. What should I look for in an amp(don't want a thumper system)? The 8 track only has wires for 2 speakers, if I add an amp could I then have 4 speakers? I am thinking of finding some better speakers and mounting them under the edge of the rear seat and possibly in the front kick panels. I am also thinking of adding a redirad so I could plug in mp3 or satellite radio.
Thoughts? Ideas? Suggestions?
Thanks
Aaron