When installing the head unit i never attached the wire labeled remote wire fromt he head unit to the amp. Do I need to when installing the amp?

 

Uh yes, lol.
That is how your amp turns on when your headunit powers on, and powers off when your headunit powers off.

 

Even if the guy before me put a switch to power the amp in? So I can turn the amp on and off when I want

 

In that case, just run the wire through the switch. Make sure you're running a in-line fuse if you are going that way.

 

Your better remember to shut off the amp everytime you leave your car, else your going to be suck with a dead battery.

 

connect your amp to the remote wire FTW. You'll never need your amp ON when your radio isn't. Just run the remote wire back. Play it safe.

 

If you want to keep a seperate switch, also connect the red wire on the head unit to the switch instead of the ignition circuit. Then you can turn the switch on and play music without the key on. This will also remind you to turn it off when you leave the car.