Do you want more sound quality, loudness, or a mix of both?
How much money are you willing to spend?
If it was me, I would probably put 6.5" componets up in the front in kicks, 6x9's in the rear deck(all amped), new head unit of course, and in the trunk would reside either 3 10's, 2 15's or 2 12's.
- Steve