Noisy is used relatively here. I have an Emperor 400 and ran it about 8 months but I could never get it quite enough for me. And it wasn't the water flow that was making the noise, it was the filter itself. Don't get me wrong, it's a great filter but to me, it's noisy.
I try putting petroleum jelly on the shaft re-seating the impeller, but nothing worked. I used this in my living room and it's just too noisy for me. I replaced it with another XP3 Rena canister filter. Now I can set in the room, even right next to the tank with tv off and just watch the fish. Very little noise.
Now if this was used in a noisy environment then maybe it wouldn't be noisy to some. But in a very quite room, it's noisy. So keep this in mind. Good luck and I hope it works out for you as they are really nice filters.