I bought a used 1/3 hp artica and have been happy with it. It's next to my tank so that makes it heat up the room ~4-5 degrees in the summer and while the noise is bearable, if it's in the same room as you, you'll need to turn the TV up a bit. My overall system is ~225 gallons and the chiller kicks in at 81.5 F. It takes about an hour to pull temp down a couple degrees, so I'm glad I got the 1/3 hp, especially since i don't vent the heat. Less 'on' time = less duration of noise, so if you can get a good 1/3 hp one I think you'll be happy you got the higher powered one. My guess is the chiller increased my electric bill by about $30/ month.