Sorry for getting a little off topic, but here a picture of my truck with the clear corners.
I'm in the process of building a new system for my truck. I used to run a set of 12" subs in a sealed box powered a Rockford Fosgate Punch 400 with the rest of the speakers running off the stock unit but my amp shorted out on me.
For my new system, I just bought an Alpine 7977 headunit. I will be powering a set of MB Quart 6-1/2" components in the front doors and a set 5-1/4" in the rear doors off an MTX Thunder 204 amp and a set of subs off an MTX Thunder 152 amp. I haven't decided on what size sub to get or how many since I want to do an install that will take up very little cargo space.
As with what superjens said, having an amp powering your front & rear speakers will make a world of difference. If you like the stock head unit and you want a little oomphhff (sp?) I would just add an amp. Just keep in mind that the stock unit does not have RCA outs so you will need an amp that will accepts high level inputs or you will need one of those low line converters.
[edit to add] Some people would argue that the rear speakers are totally unecessary and that they will be drowned out if you're running subs in the back. To me, it's all a matter of personal preferences. Personally, I can't really hear the rear 6x9's from the front seat. It pretty much sounds the same if I had the fader all the way on the front speakers when compared to having the fade controls balanced. Given this conclusion, I personally feel it's not worth upgrading the stock 6x9's. Even when I sit in the back seat, the rear speakers add little fill to the overall soundstage.[/edit]
[ 12-04-2001: Message edited by: lil_pino ]