Just looking for an audible alarm thats reliable. Just something that has a couple sensitivities... like a chirp for small bumps and going full off if someone is messing around with my car. Recommendations?

I have a 91 so already have the vats system and a kill switch wired. ALso how easy are these 'simple' alarms to wire?

 

The all in one siren & alarm circuitry units usually use current sensing & radar proximity sensors. Both will cause you a large number of false alarms.