Give it a try, and see what happens. If the voltage drops too much at idle, then swap some pulleys. I run an overdrive pulley on the crank and the alternator. The water pump was spinning just a little too slow at idle to keep the car cool with an underdrive on it. I'd try them all first and see what happens. At most, I would guess you might have to put a smaller pulley back on the alternator to get the power back up. 130amps should be plenty to power the stereo system so long as the alternator is working correctly.
Kurt