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.