2006 pacifica 12v lead

Job: Wiring a DC power adapter for aftermarket Sirius Satellite Radio (to eliminate the jack in the cigarette lighter). For 12V+, I can 1)wire it directly into the under hood fuse box using a fuse jumper (of course I have the grommet, caulk and wire ties to safely exit the fuse box) -or- 2) Find a 12V line under the dash. For 1): I can not find a convenient path through the firewall. There is the hood release cable grommet which is easily visible on the engine side right below the VIN plate. But it feeds into an impossibly tight area on the passenger side. I can not trace it once it reaches the interior. Right next to the hood release cable grommet there is a rubber plug. I am reluctant to remove it, but it might be the perfect portal. For 2): I am not sure which wire under the dash is right for 12V+. I have removed the drivers side knee bolster and the radio, so there is plenty of spaghetti to choose. I just don't want to play trial-and error. Any suggestions? Thank you in advance, Griffy