underdrive pulleys with full alternator output?

Which set/brand of underdrive pulleys have the most alternator output? Another way of saying it is, which set underdrives the alternator the least? Is there some custom setup that would work good? (eg. March crank and water pump pulley, with a stock alternator pulley). I assume that I want as small of a alt. pulley as possible, correct? My stereo eats lots of amps.

Thanks,
Rick