adding bulbs to a circuit will cause problems. when you add to a parallel circuit, it drops the total resistance of the entire lighting circuit. when resistance goes down, amperage goes up. when you raise the amperage too high on a specific circuit that wasnt designed for that much current, youre going to burn things up. so basically, by adding bulbs, youre gonna blow fuses. halos are a bad idea unless the car was designed for them or you rewire the car specifically for them.