I was just funnin...

I plan to install a 4-ch. amp under the seat and run my Zune directly into it. There will be 2 5X8's down low by the toe boards up front, 2 more right behind the seats about chest high. No subs or tweeters...however it would be my thought that a 4-ch amp pushed to some mid drivers and tweeters up front, split through a crossover mounted under the dash. Same in rear with a small mono or 2-ch amp pushing a few 10's would do the trick. Nothing super high wattage...it is a truck after all. If you put the gas tank under the bed, you would have plenty of room to mount a small sub box behind the seat, mount your amps in the middle, mount a head unit in the stock location...and the only way you could tell anything was done would be if you flipped your seat forward or looked down by the floor or saw where your tweeters were mounted.

Not much has changed in the past 30 years of speaker technology...it is still a very crude way to produce sound that is very inefficient and dated. I am sure the knowledge you have from days gone by is still effective.