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Nope. It might mean something is wrong, but doesn't tell what.

Most likely cause: voltage regulator. Next, alternator. But it could be a wiring problem.

If you want to test it, first check the voltage with the engine at 1200 rpm. If it isn't over 13.5, there is a problem. You can bypass the regulator, if it goes over 13.5, the regulator (or wiring for it) is bad.

You shouldn't need a meatier alternator. The central locking and alarm doesn't take any power from the alternator, since you generally use these while the motor's off. The subwoofer, unless it's a high-watt unit won't need it either ... maybe someone else can state at which stereo wattage you'd need a bigger alternator.