When I got my first Fluval 405, I set it up, got it running, and then had to put my hand under the stand right next to it and even then had to touch it to make sure it was on, that's how quiet it is.
I have not used the Renas so I can't say how bad they are. I have seen the layout for the media trays and they seem more complicated than they need to be. I would still use a hang on back filter, especially if you already have it. My water is much clearer when i set up my Fluvals they way I do now. The bioload can be increased with more filtration. The fish also seem to have fewer problems when more filtration including a canister is on the tank. My cousin had a large bioload in a 90 and he hates canisters, so he did not have one. It got to the point where the tank's chemistry basically collapsed and almost everything died. I strongly believe that if he had at least one Fluval 405 and did bigger and more frequent water changes, he would not have had this problem.