All protein skimmers are built about the same anymore. Everyone is copying off of each other. The trouble is, their tank size ratings are not accurate. The most important part of a skimmer is the pump- air draw mainly. The more air it pulls, the more efficient your skimmer will be. For a 75 with sump I would like to see a 700lph-1000lph air draw.
If they don't list the air draw, chances are it isn't the skimmers' strong point.