According to the performance graph on the fan review.
Any of the fans below the 1650RPM fan (which is what comes with the kit) will do better. Including the typical radiator recommendations of the Gentle Typhoon AP-15 and the Scythe Slipstream 1900 fans.
Though you may want to ask someone else for recommendations, I'm using the stock fans from my RS360 kit (which are those 1650 Xinrulians) and some old case fans I had laying around. Didnt really research that heavily into radiator fans.