I'm not sure what you're trying to accomplish...do you want a lightweight racing battery for actual racing? Or do you want something to help your stereo? From what I've seen, you can't have both.
yes you can, all you need is a gel-cel battery, which the optima is. i had a stinger battery in an old car i had, was the power of more than 2 optima batteries. cost $250, you could literally arc weld with it and i had a big stereo with it also. i changed the battery back to stock when i sold the car and i needed to get a new starter, the old one was shot, but the battery just pushed the current through anyways