depends on what you consider noise to be... im used to my remora's hiss, but when i got a coralife superskimmer, i could not stand the machine grinding venturi of the pump itself..
really depends on you and how "willing" you are to deal with noise.
so far, the quietest skimmer i "hear" is the deltec hang on mce600 as the pump is totally sealed within the unit..
but in the end, there is no real quiet skimmer as they all involvemixing air and water together at high rates, which is not a quiet thing.