The Classic series? As far as im awaire they are one of the quietest on the market(gimme a week and i'll tell you) but they are definaley very energy efficent due to the simple make up of there design. No fancy purge systems, built in heater or UV filters which also means they are ultra reliable.At the end of the day simple is best. Lets face it how many other filter manufacturers are still producing the same filter as they did 10-15 years ago????? I just ordered a 2217 for my new 67g tank btw.