While the Lian Li comes with 3 120mm fans, I'd like to replace them since the board supports 2 PWM fans.
However, I'm undecided.
1) Scythe Slip Stream PWM 1300rpm
2) Sharkoon SilentEagle SE 1200rpm
3) Noiseblocker NB-BlackSilentPRO PLPS 600-1500rpm
The Scythe Slip Stream PWM can give you fan speeds of 300-400 rpm at idle, if you set the Asus BIOS PWM fan profile to 'Silent' mode and set the CPU Fan Speed Low Limit setting to 'Ignore'. The Sharkoon Silent Eagle SE can do this too. And the Silent Eagle will run at slower speeds that the Scythe in the lower PWM duty cycle ranges. The problem I had with the Silent Eagle was that my samples had a slightly crackling bearing if you spun the fan manually. This did not seem to matter once the fans were in a system but the Scythe fan bearing was completely silent. The 12V, 9V and 7V modular cables of the Silent Eagle have the disadvantage that they have a four pin molex connector so cannot be plugged into a motherboard. And due to the molex connector you cannot monitor the fan speeds. But as a PWM fan the SE is one of the select few that can get down to the 300-400 rpm speed range under motherboard control. This motherboard control is thermally based so low speeds at idle can be combined with automatically increased fan speeds as the system load accelerates and/or the ambient temperature goes up.
As your motherboard has one CPU and two chassis fan headers I would suggest that if you do go the PWM fan route that you buy a PWM Y cable. This could be used to share the CPU fan header between the CPU fan and a PWM exhaust fan. The two front PWM intake fans could then be run from the two chassis fan headers. These chassis fan headers cannot be individually configured but potentially you could use the BIOS and/or the supplied Fan Xpert+ software to setup the chassis fans to run at lower speeds than the CPU/exhaust fan combination. Like the CPU header the chassis fan headers also have a Fan Speed Low Limit setting in the BIOS which needs to be set to 'Ignore'.
These are the figures for the PWM duty cycle ranges for the Scythe Slip Stream and the Silent Eagle SE as reported by the fan calibrator in Asus Fan Xpert. The first figure is the PWM duty cycle and the second figure is the fan rpm at that setting.Scythe Slip Stream SY1225SL12LM-P
100% 1318Sharkoon Silent Eagle SE