I had the front door panels off and was shocked and dismayed to discover that there is a special connector on the speaker. I'm assuming the ones in back are the same.
If you're going to upgrade the speakers, you'll probably have to cut the wires and crimp on a connector to fit the new speaker.
Can't tell you about the color coding of the wires. Possibly you could pull the door panels and look at the wires at the speakers to see if they're different. Otherwise you could just look for where they're routed and figure it out from there. I think the +/- is labeled on the speaker.
As for adding an amp: if you want to still run the stock head unit, you'll need to an amp that takes speaker level inputs, or an adapter to knock them down to pre-amp output levels.
good luck,
mikeT
p.s. be very gentle when removing the door panels. I broke a few of the snap rivets when I was fiddling with mine. They break pretty easily (compared to my VW).
------------------
2001 SE 4X4
Rain+Dirt!
_________________________
2001 SE 4X
Rain+Dirt!