I spliced the amp turn on directly to the ACC wire. All i did was connect the ACC wire to the AMP turn on wire. The advantage of this way is all the wiring is already close to each other. If youwa nt to go through the power supply you would have to run a wire from the power supply up which depending on your configuration could be difficult. The down side to doing it with the acc and amp turn on line is that you get an annoying pop when you turn on the car and the computer actually kicks in. You can get a delay timer thingy(don't know technical term) that will turn the amp on after a set time. As for dangers I can't forsee any dangers from using either method. Its a low amperage 12 volt signal being sent just for turn on purposes. As long as you either solder or crimp conect the wires together then use electrical tape to cover up any bare wire, you should be fine.
Hope this helps.