I wouldn't worry too much about the battery/electrical situation yet. See how everything works out first and if you do happen to see a problem, invest into a larger alternator. What are you looking to have installed? Do you need a box built or do you just need the wiring hooked up? And sound deading doesn't take away from SQ, it actually improves it. By making whatever it is applied to denser, you reduce road noise and keep the music inside. Unfortunatley, with what you have, rattling will probably always be an issue. Don't stress too much over it.