Just got a message from my local hydro shop. Their discounting inline fans 4" and some can fans. Was wondering what the noise is on one of those. They couldn't answer. Made a smart remark when I asked him something to the effect "Well their not made for submarines". quoted $44.00 for the 4" inline fan and $130.00 if I got the filter with it. Noise is the most important factor for me. Anyone ever use these?