Well the 280 i have is great but old. I just replaced 2 400's with AC
110's due to the impeller being loud and i even replaced the impeller but just too loud. The 280 i have has flow controll on it so its like 6 or 7 years old. If you havent got it yet I would just get the Aqua Clear 70. You only need 3 7/8 behind the tank for it. Dont get me wrong the emperor does a great job I have just had bad luck with them being loud except the 280.