If your amp doesn't turn on it does, but you can use any 12v source as long as it turns on and off with the key, otherwise your amp will stay on all the time and kill the battery!
I ran my remote wire thru a switch I installed on my dash so I don't have to worry about draining battery. It helps when I'm listening to talk shows or songs that don't need bass. I found LED switches for $2, but better around $6.
thats a good idea if your head unit doesnt have the available option to shut off your subs but even running a swith you are gonna have to find a accessory power supply so I would go to your radio fuse in your fuse box then to the swith then from the switch to your amp.