Here is what I did in my 88 Sub....
Alpine mp3 deck/Kenwood Sirus sat.
Changed out the speakers in the dash to sony 31/2" two ways.
I put Jenson tweeters on the pillers between the doors.
I took out 4x10s and put in Pioneer 250w 4way 6x9. I made the filler panles my self out of cabinet backing board then painted it with Plastic coat high temp black.
Then I hid a 200w amp in my center console to feed a 8" Bazooka tube. I didnt want a big box in the back of my truck taking up room. I fill the back up alot to go on hunting trips.
The 31/2 and the tweeters are run off the front channel.
The 6x9 are fed off the rear channel.
The Alpine puts out 40wx4.
200w amp just feeds the 8" Bazooka tube.
I put speaker baffles behined the 31/2 and 6x9 (look at Crutchfield.com for them they make the speakers sound a little beter)
Its not the loudest system but it sound cleen and I didnt have to cut my truck up to bad.
You cant here it 3 blocks away but after 1/2hr of cranking Pantera it will make your ears ring!