JonyB seems pretty knowledgable concerning the stereo upgrades. I agree with adding an additional battery. I install a groupe 31 for our installed systems. I also insist on installing a Battery isolator system to charge both battery's while the engine is running. The stereo battery will not drain the cranking battery with this type of install. You can go one further with a dual battery selector switch also. This will allow you to turn off the battery's if needed. Al