The factory alarm is pretty beneficial. I don't know if the 97's is anything like mine, but mine is effing LOUD. Annoyingly loud... not like those sissy aftermarket alarms a lot of people have.
A few years ago in Wichita, at a Motel 6, I had a large box in my back seat. Electronics item. Some douche broke my front passenger side window and opened the door... alarm went off, and being loud as hell, probably scared him off... because nothing was taken.
I actually heard the alarm in the middle of the night but for some reason I didn't think it sounded like mine.