Bart,
What are you doing to your poor VX?
Kidding.
Yeah, I could see how the rattle would be annoying if you can't drown it out with some tunes. So far my squeak isn't too bad, and it really only shows up when I go over bumpy roads, but I want to get it fixed before Moab so I don't go completely stir crazy on the trails.
If you don't get it figured out there is always "Red Rock Wrenching".....if you guys can make it, that is.
EDIT: BART, I just thought about this; does the rattle happen only when your interior fan is running? If so the fan may be out of balance or hitting something in the dash. Every now and then my fan will go out of whack and contact something back in the dash and make a loud, rhythmic ticking/clacking sound (and it is loud enough to be heard over the music). Luckily it goes away, but I may have to get back there and fix it some day. You said that your rattle happened when the heater was going full blast (lucky dog with all the snow) so that's what made me think of it.
"The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong, it usually turns out to be impossible to get at or repair."
-Douglas Adams, Mostly Harmless