Solid core door, two dead locks with different keys and good insurance is all that is needed. Anything else becomes a man trap and that is gonna land you in hot water.
In reality it is hard to sell astro gear on the used market. Places like Cash converters alert police straight away when they see equipment that looks expensive. Even thieves are not stupid about fencing gear off. If you have the basics it will deter most. I would not lose any sleep over whether someone is going to steal your gear or not. Get the insurance and prevent the problem in the first place.
