I'm looking to get a pager alarm, but I wanted to know if there are any specfiic brands highly recommended? I know autopage is one of them, and if I were to get one, would I have to order directly from them or find an authorized autopage dealer/installer? Also, if there are no installers or dealers around in my area, and a ordered the unit, can any stereo shop install it onto my current crappy nissan alarm system, or is it recommended to get a new alarm with it? I've seen other pagers that can be installed onto the current alarm system.