wow yeah thats quite a difference in amps >.< and thats how you blow a fuse running that with the halides, do you know how many amps your system is drawing already? that would be a big concern too, thered be two routes id go, bigger is better most of the time so i would want the bigger of the two but that would mean that changing the electrical would probably be the better choice for tbhe 20 amp circuit. or running the plumbing for the chiller to a different outlet even if possible. Do you use any fans on the halides or anything to lower temps too or just the chiller, and how precise do you plan on letting it run? with no fluctiations?