You really should keep your reservoir at 62-65 with those systems. Helps to avoid algae, pH creep and slime build up. Buying a chiller just for that would be kind of a waste of money though. Just freeze some water bottles and stick one in every few days or whenever you need it. If you bought a chiller you can not run your nutrient solution through the chiller. You would need a 1/10hp chiller, 20 gallon reservoir, pump, and a cool coil to run the chilled water through while it sat in your nutrient reservoir. The chiller only chills its reservoir. You then use that water to chill equipment like the coil.
Sorry budley but your statement is off. Chillers are used for a TON of systems from ANY hydro setup to efficient cooling systems.