JW Air Pumps are fairly quiet air pumps. It has a patented design that absorbs vibrations from the ballast. Models 400, 500, 600, and 700 have an adjustable airflow. Models 500, 600, and 700 also have 2 outputs (the flow knob controls both outputs at the same time). These pumps have a limited 3 year warranty.
On the back of the box, these are the recommendations from the company on how many air operated ornaments, filters and airstones it can operate:
Model 200 - 2
Model 300 - 3
Model 400 - 4
Model 500 - 7
Model 600 - 9
Model 700 - 15
Rivers to Reef says: We really like these pumps. They are pretty reliable as far as pumps go and are pretty quiet. Please remember that these are air pumps and they do vibrate, so they are not going to be completely silent. When it comes to sizing these pumps for peoples tanks, we really don't understand what the company is talking about. Who runs 15 airstones, filters, and ornament on their tank?
Picking the right pump is a matter of water depth and what you are trying to run. Deeper tanks require more pump strength. We really like the Model 400 for standard tanks 40 gallons or less where you want to run 1 - 3 filters. The reason we like the model 400 is because it has an adjustable output, so you can turn the air flow down for smaller tanks. Model 700 can do really deep tanks. We use it to run two sponge filters on a tank that is 27 inches deep.
So here is a ballpark of what we recommend. If you are worried that your tank is really deep then you should probably get a bigger air pump. If you want to run a gang valve on any pump, you should probably get a bigger air pump.
Model 200 - 10 gallon tanks
Model 300 - 20 gallon tanks
Model 400 - Tanks 19in deep or less (29, 40B Gallon)