Sirius users have a 2 receiver distribution kit available to them. (
Link here
) It uses coax cable from the antenna to a coaxial splitter. I don't know if you can get away with splitting the signal six times off a single antenna without an active amplifier but you may.
Worst case scenario would be getting three of those kits but you may be able to get away with 2 or even just 1. You might also ask over at
SiriusBackstage.com. They have some pretty hardcore subscribers and installers that may be able to help you out if you don't get the info you need here.