I bought my matrix 3.5 off of Ebay for $260+20 shipping. 280 is cheap for a good alarm. Add in battery backup, hide your components, fuel switch. You'd be fairly safe.
<<<<Battery backup, piezo sirens, paging alarm, remote start. A nice option with the 3.5 is the factory arm and disarm stuff is built in. There are very few add ons that are needed. That is unless you want the one minute timer on the dome light and the trunk popper option. They are options, but require extras.
Relays and solenoids are not included. It will pop your locks and start the car. It will also blink your flashers, etc. I added a motion/tilt sensor in case someone started slowly jacking up the car to steal my rims. About $40 more.