Had to laugh at this. Maybe in 2010 this was true. But now with the oil field boom you can get car jacked in ND. but all things said in this thread are good ideas to secure your system. I had mine jacked 20 years ago from my Camaro. All they took was the HU and CDs. Didn't touch the speakers, sub or the amp. $400 HU and about $200 in CDs but left $800 in the rest because harder to get to. Only other time had my car broke into they took 9 packs of smokes and $3 in change.
Now I have a 79 International Scout, easiest vehicle to break into and top is always off in the summer, but most wont even touch that. Its lifted to where you have to be over 6' to see into it. And then you would only see speakers in the door and rear seat along with a sub box and amp in the far back with NO HU. That's hidden behind the glove box. And I mean behind the glove box. Took out the inside and shortened it and placed the HU above the defrost hose with a wired remote mounted on the side of the center console. Most don't even know I have a HU until I turn the scout on. Sub box it bolted down so the subs/amp are an inch from the rear seat. (unless you know scouts you wouldn't know the seat folds down for access to the subs and amp and mounting bolts. back of box is hinged so it flips back when you remove the front bolts.)
I work in a prison and have run into many ex inmates that have looked at the setup and none have figured out how to remove the sub box lol. Not saying its the best setup but whole system is only worth about $700. So not too worried about it. Its insured for double that price. Hoping someone does steal it so I can use the insurance money to get some better marine speakers for off roading. lol