What I did for my 8500x50 was mount it above my rear view mirror, as shown. Yes, that's some heavy duty 3M velcro that I never trimmed. The stupid suction cups kept falling off, so I did this, and have been really happy with it. Note: I also put some of the soft velcro on the bottom of the passport to keep it from bouncing off of my rear view.
I ran the power along the head liner (you can curl your fingers around the upper lip of yours if you try... there's a nice place to lay a cord in there), over to the a-pillar (this pops off rather easily, just check any of the Z forums if u need help), and then down to the fuses. Pick a fuse that's triggered on/off with the car (again, forums if u don't want to check w/ a volt meter) and a decent current (15A is good). Find that wire in the back of the fuse box, remove some of the shielding, solder on your end, wrap it all up with some electrical tape, and voila.
If you know what you're doing, this takes 15 minutes. If you don't know, this takes an hour. If you go to some place to have them do it for you, I can't even imagine how bad they'd rape you, 'cause it is instantly obvious you don't feel comfy with car electronics.
(Side note: the low voltage reading is 'cause I was a ****** and soldered it to an "always on" circuit, so I have to manually turn it on/off when i'm in the car. Normally run 14.8-15.4V)