I would get a 2-way alarm that has a ton of customizable options. I have to stick up for my Ultrastart! Ultrastart also has very good range, and everything I've ever read about them has been great; that's why I went with them for my remote starter. I can start the damn thing from inside my office at work with my car being a few blocks down the street if I want to (tested that a couple of times). They also have a crapload of options. I believe that it's comparable to Compustars, but just cost a bit less on average (just based on researching this stuff a lot when I was in the market for one).
Here's a link to one of their best systems. It's a 2-way with just about every feature out there (they also have a number of other systems with varying features):
http://www.ultrastarters.com/4560.html