Sirius - Power Supply
Seems weird that the power supply does this voltage drop. I hard wired my sirius (different model) directly to the accessory (from the radio). I also did the same for my i-pod (monster ipod converter).
But regarding your question yes it can be done and there is some room behind the radio (location i put my monster i-pod converter box) where you could put it.
Assuming that you have some basic wiring skills it is fairly easy and you can just splice into the existing cig/accessory power location). No need to go back to the fuse block. Afterall these types of components do NOT draw alot of amps.
Igo, CA (Near Redding)
2004 Liberty (3.6 v6 gas) - Rocky Mountain Edit - Silver/charcoal