Hi Hun25,
I am in the same situation trying to find a quiet pump. I have a Mag 9.5 and it is much quieter than the RIO that I had. I can't really hear it run over the noise of the cascading water running down to my sump. I am happy with it however I needed a pump for my protein skimmer so I was again in search of a quiet pump. I had heard a lot of good reports of how quiet the Quiet One was so I purchased one with about 700 GPH output. When I received it I was stunned to hear how loud it was. I sent it back thinking that it was a factory defect, however the next Quiet One that was sent out turned out to be exactly the same. Being satisfied with the Mag 9.5, I ordered a Mag 7 for the protein skimmer. It was quieter than the Quiet One's by a long shot however it was noticeably noisier than the than the Mag 9.5. Maybe I will try a Eheim as I have heard many good reports on them, but I am worried that there are maybe just some good ones built while others pumps of the same model will be noisier. That is the only way that I can explain the poor performance of the Quiet One when I had heard some much good about it and the noisier Mag 7 when it comes from the same line as the Mag 9.5. All the best and if anyone else has experience with a consistantly quiet brand of pump I would be interested to hear this type of experience as well.
Thanks,
Haakon