Aftermarket DVD Nav. software......

I've searched this forum high and low for hours and couldn't find an answer so here goes.....

With the factory navigation system is it possible to use aftermarket software such as Delorme or Rand McNally for example or does it only read Nissan/Infinity discs? And if only Nissan/Infinity discs, are there updated versions available and at what cost? I've only had the truck for about a month now and I've already traveled into areas where the factory unit does not provide much, if any, information. The streets in these areas change to green (day screen) with no names and the voice guidance warns me that I'm entering an area that they pretty much have no information on. And were not talking about dirt roads, these are major through-ways...state roads, U.S. highways, etc....that just happen to far away from any major metropolitan areas. You know, the kind of places that you actually NEED directions to.

Thanks for any helpful info, any and all answers are appreciated.