[donv]

It's been a long time since I did the rear speaker kit, but if I remember correctly, the male terminals on the back of the radio were simple flat blades. You might consider going to Radio Shack or Fry's, etc. and get solder or crimp terminals that match. Then you could make the harness up outside the car and just insert the terminals into the connector block. Yes, tedious doing it one by one - but easily swappable if you get something mixed up, and no hot irons and molten metal near all that expensive plastic!

On the earlier question re: negative ground, I'm fairly certain you're safe there based on the wiring diagram and it being a modern car. However, you can easily check it at any bulb location if you use a DC voltmeter to be sure.

One caution: try to use the established electronics ground that is in the dash area (the radio harness being a good source) instead of any random chassis ground. I can't explain the difference, but there is one. You may end up with an ignition noise issue if you use a chassis ground (there are filters that can fix this, but why go there?).

Good luck!