I have 2 400 on the 75 and a 280 and an ac50 on my 55
1 of the 400 is about 5 years old and i had to replace the impeller its never been the same
The other 400 is 3 mos old and was loud out of the box so i called and they sent a "repair kit" inpeller and housing still loud. I called again and was told to unplug and plug back in untill it got quiet. Well this worked but a day or 2 later i have to do it again. Its a shame because besides that i really like it.
The 280 uses the same media and its even older and has flow control Its silent.