I get terrible reception with my Sirius reception with the stock antenna, anyway (even in the open desert). When I complained to Sirius, they said to move my antenna - I asked, "You mean the one Dodge drilled holes in my roof for at the factory?!"
You may be better off with an aftermarket antenna (even if you don't currently have any reception issues).
At least our antennas aren't as ugly as those damn tumors on Chevies. You're having to ask where the antenna is speaks for how well it is concealed.