the rating the suppliers give is a guideline. It depends also on your bio-load. How many fish, do you feed frozen foods, feed fine food to corals etc. So yeah, bigger is better, but it does not wok to go too big. You need enough foam to fill the skimmers neck.
A TS3 will work. I had one for a while running. The Reef Octopus NW is also good. At the end of the day its a personal preference. Also check out the for sale section.