Dude,
My recommendation is make sure that your insurance company will reimburse the car and all accessories that you added to your car. I have Allstate and they cover all mods as long as it's permenantly installed on the car, I have the receipts, and pics of mods.
For alarm, yes...alarm might help, but if they want it...they'll get your car! What if someone comes up to you while you're in your car, points a gun in your face and says "give my your car!". Well, your car alarm is worthless now! And, possibly your insurance company won't remimburse you of all the mods. So, car alarms keep the honest, honest.
Just some tips.
Dennis