Wow, that was fast.

I do like the idea of a safe in the trunk. Years ago, I'd seen other cars with pullout stereos that have something similar. Pull out the stereo, lock it in the safe in the trunk, "stealth" the dash, and you're good to go.

Which is really the only other thing I would recommend as far as theft prevention: The Stealth approach. I did this on my VW GTI and now on my Honda (Pictures here). Highly recommended.