I have a really stupid idea to turn one of my old backpacks into a 300w portable speaker. I plan on using an 8 inch Pyle subwoofer and a few mids and tweeters. I want to know how to wire a car amplifier up to run off of a battery (if possible) I don't exactly want to lug a 14 pound car battery along with a good 30 or so pounds in other materials. Any tips? If not then I might use one of the cheap China eBay amps (Lepai and other brands) because those run at 12v 7amps which is manageable. Problem with those is that they won't put out the full wattage then. Any tips?