Hmmm, I think you have it backwards.
http://www.marinedepot.com/aquarium_chillers_titanium_arctica_jbj.asp?ast=&key= Using these numbers I get the cooling amount of the 1/3 HP one is 1,172 watts of cooling. It says it's 7.25 amps though, which would make it about 830 watts of power usage. 1/3rd HP is about 250 watts. Ok, I'm confused...
But anyway, I think at 0 temperature difference that 400 watt chiller would be cooling more like 1600 watts, wouldn't it?
*Scratches head*