A good security system won't keep you up at nights. When you have a good security system in place you can concentrate your energies on your own business, and let your defense systems do their job. The thing to consider when setting up your security system is to carefully balance the cost of having a weak system in place versus the cost of operating a strong system. Weak systems are actually preferable for low cost assets. Strong systems should be reserved for high cost assets.
When doing your cost-benefit analysis consider the productivity lost by having too many passwords or too many key-card entry systems: they slow down your staff, and can prevent access to legitimate personnel when they forget or misplace passwords or key-cards.
Also consider the internal threats versus the external threats. In larger organizations especially, the internal threat can sometimes pose a greater potential risk.
Given your situation, you may need to employ some or all of these technologies: