I went with the Polaris Slingshot security system. The system is made by Scorpio but is completely plug and play for the SS. Part number 2881815. It did not want to splice wires, so I just went with this system. Directions could be better, but it is installed and works great.
I understand the unit plugs into the existing radio harness. Would the same alarm unit work with an aftermarket sound system? I no longer have the original radio harness.