The best place to take a feed in terms of ease of fitment and proximity the to the upper dash would be behind the head unit. Im pretty sure youre gonna have trouble getting a wire between the dash and windscreen without some sort of modification though. Are you sure you want to have a sat nav on permanant display to every thief, crook and scumbag???
I saw a mod like this done with a tomtom one in a Ford C-Max, In that case, the unit was mounted in the fold down sunglasses holder in the roof. Wiring was run between the screen and the plastic edges or roof panel. It just pushed into the gap. You may find that you could run a cable from a power source under the dash, around the edge of the dash and up to the middle of the dash by just pushing the cable between the panels. You shouldn't need to move anything. I managed to fit a reversing camera screen on my rear view mirror by using this method.
Im looking at the same thing in my 156, idea being I hate the power cable coming out of the centre console and banging my hand every time i change gear. Just looks messy. possible to come up through the air con ducts or ?
could do, but it'd be a nightmare, you'd have to get to the pipework. cut into it and make sure the cable doesn't interfer with the flaps inside, you may well be better off putting the cable between the cdemister vents and the dash, maybe remove the vents, cut a little hold for the cable and then refit. Again getting to the underside of the dash would be the problem.
when running a cable to the CD plater in the boot of mrs Ps selespeed, there is loads of room above the fuse box flap, so I would mount it on the screen pillar, poke the wire though the gap where pillar meets dash, grab hold of it above the fuse box and pull through, take out the radio, feed the wire from the fuse box area to behind the radio and then connect. There is loads of room behind there. Connection wise, what about he cigarette lighter? pretty thick wires, but I cannot recall if it is switched.
Cheers Guys. As suggested I was thinking of coming through between the dash and the a pillar, I was just wondering if there is anything near there to wire it in too. I did the same on my Fiat Coupe but used a feed from the dash light dimmer controls.