When I fitted the GPS to my Adv, I tee'd into the power socket
wires alongside the dash.
Agree with the scotchloc criticisms, I use a crimp on tube connector that has a heatshrink outer and contains a glue. You crimp it on, get the industrial hairdryer and it heatshrinks, glues and seals the connection. Made by Wurth cost about a quid each. Totally reliable.
Ref the Ferrari stereo install, we did a £56,000 Alpine F1 status install into a Jeep Grand Cherokee last year. It was a great project, took 5 months!! Not rushing to do another..