hows this,
i work at best buy, and i own a 95 burb. (crazy huh?) i just dropped a system in. ill give you some pointers. ditch everything stock!
that being said, the rest is up to your budget. the 4x10's in back will suck regardless, its a terrible speaker design. the pioneer ones will work ok as a replacement. the 6.5's can be replaced with whatever you can afford and think sounds nice. you dont need an amp. anyone that says you do is a moron. if you can crank a 50wattx4 system in a burb and tell me its not loud enough, you need hearing aides. if you want subs, then you will NEED an amp. again all this depends on your budget.
the most important thing you pick out is the head unit (cd player) pick out one that has mp3 support, and has preouts for subs with all the adjustments and crossovers built in. (the pioneer 7500 is a nice one) if you can affordin dash dvd, go for it!
lemme know what you decide.
-Rob