$600-$700 is a lot for an alarm IMO... Is the car and the stuff inside worth that much t drop that kinda flow on it??? Look at it his way, if your car does get jacked, do you want to be out the money for the alarm (a lot or a little) PLUS your deductible??? I mean if the car was worth like over $20G's and is a forsure theft magnet (i.e. ITR), then I'd spring for an alarm over $500, but for an Si like mine, I'll pass... My $300 Viper is plenty enough to make me sleep easy at night. All an alarm is doing is buying you time and peace of mind. Some people require more peace of mind and thus pay a lot more for their alarms.
But for that price range, I'd look into Compustar's. I've heard good things about those....