Regarding the tweeters in the car, they are easy to get rid of. One of the first things I did when I got my rav was getting rid of al the junk stock stuff and throwing in some sweeeeeet infinity kappa component speakers.
The wiring for the front speakers is as follows: In from the side of the door, up to the tweeter, down to the main speaker. So ... when you disconnect the tweeter, it disconnects your main speakers. You can clip the wire for the tweets and send it down to your main speakers easily - you can buy terminal connectors to be crimped onto the speakers at Radio Shack - they work great.
As for those of you interested, You DO have to purchase an adaptor from crutchfield to fit new, non-stock speakers into any of the holes in the doors. A crossover fits perfectly when screwed onto the door itself, on the opposite side of the arm rest - its dry, and there is plenty of space.
Just remember to check for wires behind the spot you drill through when putting in holes for your speaker adaptors ... you DON"T want to drill through them!!!
ENJOY!