You make a fair point graham, but there is more to it than just water flow. If the filter is off the temp in the filter is no longer regulated. And while 95% of the time it may be fine, in a heavily stocked tank a filter crash can be disastrous. It just doesn't seem worth the risk to me. Lining the inside of your cabinet with soundproofing would seem like a better option to me if you are worried about noise.