i've got a viper800esp and it's great. i went with that model because i wanted the 7 channels to play with. when picking your alarm it really comes down to what features you want. keep in mind that the sensors and whatnot are just extras that you add on to your alarm. you wanna look at the basic features of your alarm (inputs/output channels etc.) and the programability features you think you might want. you can buy a pretty basic aalrm and add a whole bunch've sensors if that's all you want.

-marc