I have the R-100 on my 75 gallon and it works well for me. The only issue with the sump I had was the return chamber in my RS-100 was about 1/4" smaller than what the specifications from the retailer stated (not sure if this was a manufacturing error or website error) so I had to put my return pump in the skimmer section and drill a hole for the nozzle to pull from the return section, worked out fine in the end. The skimmer section is very large on these sumps so you have room for just about any kind you want, as well as bio-media or media rectors and the filter sock area is also large enough to fill with bio-media or live rock as well. There are sumps on the market with larger refugium sections just so you are aware if that is something you are looking at. It is also extremely quiet, no noise comes from sump except the hum of the pumps. Here is a picture of mine with an Aquamaxx CO-1 skimmer inside so you can see how large it is for reference.
