You can get good sound(high, mid, and bass) if you split the speakers up, i.e., installing your tweeter and mids in the dash, and bass speakers in the doors. If you have wing windows, you can run a 6.5" speaker in the door w/o having problems with the window hitting the magnet. I will post a pic of the door speaker tomarrow

In my '91 I plan to run something similar, but rather than in the door, I will put the speakers in the rear section(in the middle of the rear two seats) of custom center console I am building, similar to what is in 2 seater sports cars like the Viper. This way I don't have to have two sets of door speakers if/when I build 1/2 doors for it.