my tweeters
if you have really good tweeters like myself, you can put them under the headunit. Makes for a VERY EASY install, i can help you with a how-to. It is kinda like adding a center channel speaker. One thing i dont like about our cars is the fact that the speakers are on the doors (on our sides) and nothing is coming from the front or back. So this was a great addition. Then just wire them to the front speakers.
edit: btw my tweeters are the pioneer 3/4" silk dome tweeters. 50-75 bucks i think they were. Very good tweeters. Like 90w peak power.