Audio Systems: 2000 Grand Caravan, rick stock, stock systems

Question
Do the 2000 Grand Caravans have some sort of device that keeps the volume from going to high?
I'm 99.9% sure it's a basic unit, not the Infinity one.
When I crank the sound up the speakers respond but then automatically lower back down, almost seems like they have something built in to prevent blowing them.
I'm replacing the stock unit with an aftermarket one (what I have now does not have a CD or changer options) but will I need to also buy better speakers or will this problem go away once I pull out the stock unit?
Any insight you have is appreciated.
-Rick  

Answer
stock systems always suck, don't they! sorry took so long to reply, server was down. your new system will act and sound much better, but eventually you will insist on better speakers. go to crutchfield.com (to shop, not buy, their prices too high) where you'll find what fits best in your car by make and model. their site works well, very informative. hope this helps, G......