I had the model 4, no noise coming from the returns due to the enclosed pipes and also reduces gurgling from them, refugium space is big in this model, I used as a deep sand configuration and as well as a refugium, the lid there helps to put the light of your option without getting splashed, fit nice the Coralife refugium light fixture. You can remove the bottom plate before the refugium and have it configurated as a Berlin method. The last stage was a nice space for my sro300 skimmer and the Rio pump.
The only flaw I would say about is that the acrylic is thin, not compared with a custom made sump wich always seems to have cast acrylic and look sturdy than this one.
There's one for sale now here, I would say go for it, I paid 300+ for mine, wich I let it go with my 150g