Have you added an aftermarket security system?

Just buoght an '04 Frontier King Cab and it has no security system. I'm considering a Python 460Max installed by a local dealer. He wants $300 total including installation. I can order the unit for $85.00 myself. I almost think $300 is an overkill for a Frontier. If I could order it myself and pay someone to install and get out for under $200 I'd go for it.

What are your experiences in an aftermarket system? Which one did you get? Are you happy with it? What would you do different next time?

Thanks in advance!