Yes, the roof speakers can be replaced w/o a new amp, but regardless of what you put in the rear, they won't make much of a listening difference. They fire down into the rear hatch area, and won't make a huge difference in the overall listening experience. I currently have Polk Audio speakers back there w/ the tweeter facing the through the forward part of the grill,(where there is currently no speaker). But by far, the biggest sound difference came from replacing the front speakers. I am running a full custom system, two amps, one for the sub, one for the regular speakers. And I can fade out the rears and it doesn't sound much different. Remember they are only fill speakers, and that is why the factory made them so small, they don't make much impact. The reason some people think that replacing the rear speakers in a stock system makes a difference is because the fronts are inadequate to begin with. If you only replace the rears, of course they will stand out more, but you aren't addressing the fundamental problem of what you primarily hear. If you replace all four,(6 if you include one of the tweeters in the door), that is where you will apprectiate the difference. I have long said I would post some picutres of my system, but I need to get off my butt and find a scanner. I put the amp beneath the rear floor and raised it up about 3 inches and custom fabricated a sub enclosure on the drivers side rear. I needed to keep the storage space, as I often take my dog with me. Good luck, Bob Hanvey