I don't often recommend Cooler Master fans, but you might want to also consider the Cooler Master Sickflow 120's. They have a pretty high static pressure of 2.94 mmH2O, a very good 69.69 CFM airflow and only a 19db decibel level. Bearing life probably isn't as good as the Noctua fans, by a long shot, and the sound "pitch" might not be as acceptable, but if you're not extremely sensitive to pitch variance and don't mind replacing them in two or three years, they're probably a much better choice than the SP120 performance fans that come with your cooler, at least as far as noise goes.
They're also a lot cheaper than the Noctua fans.