DrZy,

I have a JBJ Artica Nano chiller that can drop a 40 gallon tank 8 degrees below ambient temperature.

I also have another suggestion that I think you should investigate for your whole home, not just the area w/ your tank.

Radient Barrier.

it's installed on the inside of your attic, and is sort of like a thin layer of tinfoil. My parents have this installed in their attic and I have stored a christmas tree shaped candel out there in their attic for 5 years and it has never once melted. When I go into their attic I am always amazed at how cool it is, nothing like the sweltering inferno that was the attic in the house I grew up in.

it could end up saving you a lot of money if you have it installed in the roof over the entire house. (lowers your cooling costs)