The 1300RPM model should be quite nice. Personally I haven't had a 120mm fan that can honestly be called silent past 1200RPM, so if Thermalright's numbers are true that'd be the one to get....
Although they are hardly famous for value and with the likes of Yate Loon, Xilence and Xigmatek all offering very good fans for not much more than a fiver (under in most cases) they have alot of competition.