In my experiemces with car crashes, I'd rather be the one insured by State Farm than the one hit by a State Farm insured vehicle. In both of my crashes (one a total loss, the other a minor bumper bender), State Farm did me right within a couple of weeks, and then went about settling the crash out with the other insurance company, without me taking a rate hit, since neither crash was my fault. IN fact, when I totaled the Plymouth Sundance, I actually got more than Blue Book value because of some custom work I'd done on the car. But, at the same time, I had informed my agent of the custom work (engine work, alloy wheels, stereo, security system), and the custom items were included in the policy.
Back to the OP, did you have all of the custom stereo equipment on the policy? If not, the terms of the policy ( a contract, after all), will cover what the car had when it rolled off the assembly line.