Clifford and Avital are all made by DEI but are the best out there. Viper is just a hype product and is actually one of the easiest to brake into. Knowing people that jack they tell me they cannot get into clifford or avital. Their most expensive alarms are between 500-600 dollars. All the extra features like the pager and voice thing and extra motion and shock sensors are all extra money. Its all on what you want but with base companies i would go with them. my .02 cents