I believe that the pre-2005 models had the rear speakers in the cargo area. I know that that my old 94 Pathfinder had them on the roof (which I thought was pretty cool). So, there are options, but whatever route you decide, it will have to be a lot of custom work. I really like the idea of having them above, but I'm not sure how you would do it.

For me, I will have the speakers in the stock locations. My seats are usually up even with the dog in the rig (I have a beagle so she's fine sitting on the seat).