Better Quiet Case Fans? Noctua NF-A14 PWM or NF-A15 PWM?

[dcunited]

They are going to be used in a Fractal R5. I know they are supposed to be used primarily as CPU cooling fans, but the Noctua descriptions I've read said they can double up as a case fan.

Pulse Width Modulation (PWM) fans and that are quiet are a must. I want my PC to run at 33 decibels (dB) or less when idle or under low loads.

I will have an:

i5-4690k
Noctua D15
Asus Z97-A
MSI GTX 970
Fractal Design R5

and,
8GB Ram
500GB SSD.

This will be my first build on my own, and quietness (less than 33-35 dB) is a must for idle. I plan to do light/moderate OC so a i5-k and Z97 is a must.

Thanks!

 

[gilbadon]

Keep in mind, without a splitter you can only have a total of 4 PWM fans in your case (plenty for most).
I Would get the NF-A14 PWM, the 150mm one will not fit in most cases.