The viper 5900 is the latest and greatest. Just got it installed last week and let me tell you this is a serious alarm.
Clifford is now owned by DEI which makes the viper so their top of the line alarms are pretty much the same but viper has a $2500 deductable remiburstment if you car gets jacked.
If you want to bring it down a notch the viper 791v is almost the same but the two way paging has a fraction of the distance.
Also, go on ebay and find a pair of whelen TIR3 led strobes, a dei 506T (glass break sensor) and two or four dei 513T (Piezo "Pain generators" interior sirens)and a backup battery. You could get all this extra stuff for about $200.
Have the installer add a relay to the horn honk output (continuos), on that relay put the peizo sirens and the strobes. With this it will fuction like a normal alarm with 2 way paging and remote start, but when the alarm goes off the strobes going off in your face making it impossible to work on anything in the car and the sirens, well one siren is enough too make it unbearable 4 sirens is brutal.
The Whelen TIR3 are the real deal when it comes to strobes, the are small, have a metal base with a solid impact resistant plastic cover, you could screw them into the metal of the pilars and it would take some force to get them out. Get the blue or red ones to attract the attention of the cops.
I hope this help, since I got my car broken into last I am doing everything for it not to happen again.