I've used Rainbow Lifeguard Quiet One pumps before. They're definitely quiet, but they aren't very reliable for reef use IME. The motor tends to sieze up after a few months. Also, they transfer A LOT of heat to the water, so beware of summer time.
I recommend Iwaki pumps instead. MD30 series on down is quiet, powerful, and cool.
I had a similar bad experience with the old pump too. The motor siezed up and the pump was poorly contructed. They used a romex connector to attach the power cord to the housing. Cheap bastiages.
I agree with len on the iwaki's. They are good pumps. A magdrive wouldn't be bad either.
I have a mag mounted internally in my sump. If you do this, be prepared to put a good bunch of foam underneath of it.
Using the suction cups that come with this thing isn't enough. The vibrations make a bunch of noise. I folded up about 1 1/2 inches of foam under mine and its nice and quiet now.
