Can I just hook up the remote turn on to a positive feed so I can turn it on and off manually with a switch?

 

sure can.

 

You can also buy a relay and connect an ignition wire to the relay to trigger it , when you turn on your key, the ignition wire will get power and it will trip the relay and give power to your amp. Check the max amp draw of your amplifier and buy a relay that is slightly bigger, if your amp draws 25 amps then buy a 30 amp relay. You won't forget to turn it off if you do it this way.