IM JUST BOUGHT A 93 GS300 AND I WANT TO INSTALL AN AMP AND ANOTHER SUB, CAN I STILL USE THE FACTORY AMP AND FACTORY SUB ALONG WITH THE NEW AMP AND SUB IF SO HOW CAN I INSTALL THE NEW AMP AND SUB. I WANT THE FACTORY AMP TO POWER THE STOCK SPEAKERS AND THE NEW AMP TO POWER JUST THE SUB