I had a stereo, equalizer, power booster and a bunch of cassette tapes stolen out of my car when I was a teenager. I was at work when that happened.
Cops came, did nothing.
I removed the case screws on the replacement stereo and screwed razor blades on the case.
A few weeks later, I come out of wok to find blood in my car. I called the cops, and told them what I had done to my stereo. He laughed, but told me that I might have put a target on my back. Never had another problem.