Thinking about turning my tank into a coldwater one

[Coldwater]

Lately I have been thinking about turning my 73 gallon into a local tank. My 33 is doing very well and I wanted to go bigger. Some of the fish I find at the beach are so much cooler than tropical ones. Also I wont need to buy expensive fish anymore. All I need to do it is get a chiller. What type would you recomend? I have been researching them and they all are so expensive.. any cheap good ones out there? Thanks

Matt