Personally, if your'e going with a Bubble Magus, I'd strongly suggest you look at Seaside Aquatic's ES5 on Amazon. Seaside takes the BM body and replaces the chinese pump with a Sicce skimmer pump, which are known to be ultra-reliable. And you can get a replacement pump from Sicce if the need ever arises without having to depend on SeaSide Aquatics. I have one of these running my 50g system, and it is absolutely quiet.
A DC powered skimmer is more money, but uses less electricity, and at least in theory, is quieter. But they're very expensive at the moment (that will change), and in my opinion, they're too new to assess the pump reliability. And a replacement pump is most of the value of the skimmer, so it's going to be really expensive if it dies and you have to replace it.