Ok seriously, the sterio system sucks!
A new deck is a must.
Speakers: the fronts are 5 1/4" and the rears are 6.5" there is a depth of 2" on both. Lots of speaker brands can be dropped in. They also have this light door lining that keeps the sound crisp. I would personally recommend getting some point source speakers, point the rears toward the hatch to bounce to the front and then disconnect the factory tweeters. And you are done....