Feel your pain, guys.
I know a guy who actually makes money by breaking into people's cars to show them the weak points in their security systems, and how to make them better. He'd tell you this: no matter what you do, if they want something bad enough, they're going to get it. The point is to make it that much more difficult.
Do like they do up in Harper (Detroit): solder razor blades on the back and undersides of your radio and amps. This way, at least the flockers will have to bleed to get your chit.
The 24kV to the doorhandles would be too dangerous. First damn little kid touches your door, it'd land your azz in jail. Bulletproof glass would be a better idea.
My little secret: I take the distributor rotor with me if I park in one of those 'hoods.