I agree with Randy. The only reason you need a chiller is if you can't open a window, run the AC, or blow a fan across your sump.
The only reason I have a chiller on my classroom aquarium is that there is no air conditioning and nobody to open a window. Ambient temp in the room is easily 95 degrees on a day like today.
Also, chillers are definitely not a DIY project, (unless you're an HVAC guy...)