JimC

Can you get the Sirius upgrade for my 2006 Pony, like is available in the 2007 using the Shaker 500?

Partscheap

That would require some serious wiring and i'm not sure if it would be possible. The sirius antenna is mounted on the trunk lid, you would have to wire all the way back there and drill a hole in your bumper trim. You may want to try an aftermarket solution if you are looking for satellite radio, Ford has not yet released any sort of kit to accomodate a retrofit and we do not have the resources to do R&D on that scale of project.