Dash speakers are (almost always) never a good spot for speakers. Doors are better. The problem with dash speakers, is you get a "smearing" effect to the sound because you now have two sound waves hitting your ears at slightly different times. 1. The sound directly from the speaker and 2. the sound being reflected off the windshield. If you can mount your tweeters somewhere near the bottom of the A-pillar in the door, and then the mid/bass speakers in the stock door location, that may work well. Or, if both door locations are unobstructed from you, then go that route. I have my tweeters mounted in the dash in my WJ, in the stock locations, and I'm pondering moving them. I can hear the loss of quality compared to the rear door speakers (when I listen from the back seat). In my SRT, I'm planning on mounting the tweeters in the doors, right near the bottom of the a-pillar. Ideally, you want them as far from you as possible, to minimize the amount of difference in distance between them. Some of the better head units can compensate for this with a time delay on some of the channels, though.
