just make it as unstealable as possible. Bolt it down with bolts on the inside of the box. Use screws that require a special bit to screw down the sub. Hopefully you have a nice 2 way alarm already.
As soon as my honda gets up and running, that bitch is getting viper smart start so i immediately know anywhere if anything is happening. So tired of thieves breaking into my shit its almost not even worth having nice things anymore.. Also, the honda is 100% stock and i'm still that paranoid. My truck has been broken into 3 times in the past year as well -_-