We already have the XM radio working over wireless FM. She says she can hear what I'm talking about when I asked, "doesn't it sound like it's coming through a tin can with a sock on the end of it?" And I can play commercial FM broadcast music and it's obviously better, and she can hear that. Still she says it's good enough. And she's right when she says that it's partially just because the XM source sucks. It's low bitrate compressed digital music after all.
The improvement with the jazzy board I'm sure will be noticeable and better, but it will never be as good as a CD or even regular analog FM broadcasts. That's just a limitation of satellite radio. Part of becoming an XM (or Sirius) subscriber is deciding that the lack of commercials and improved programming choice is more important than sound quality. I might just need to get over it.