Don't give up so easily. First, your friends should ask why they want to use the SUV's built-in speakers for the PS radio system. It's probably a much better idea to keep the systems separated for any number of reasons. Second, any seasoned radio installer can figure out a way to use simple 1:1, for example, isolation transformers on the "no ground" XTL audio output. Then they can have AM/FM audio, or XTL audio, but using the same speakers they'll find it hard to devise a system that will give them both at the same time. But again, who would really want such a horrible mish mash of sound when trying to hear the dispatcher. Just doesn't make sense.