Any of the dc pumps will be pretty quiet. The smaller ones like dc4000, dc6000, is almost silent. The eheims are quiet too, if u put a rubber pad under them. Also any of the askoll based block pumps like the airstar or red dragon are quiet too, even the cheaper laguna alternative. Remember any pump that's stronger than 1kgph even the good ones, will make some kind of noise, good smaller pumps under 1kgph will usually be almost silent.