SPCR

Should I replace them with say, Noctuas (dunno which ones) or it will not even be noticeable? Will I notice less noise? what changes in cooling can I expect as well?

I think the Fractal Design fans are decent. Occasionally, you get a bum one. Have you slowed them down?

Fans are something that are very peculiar to each person, tones are for some fine for others are bothering. I own a R6 and tested the fans, they are ok, but i still change them toward BL067 that have a smother tone (to my ears), but i would think for vast majority of users, the included fans are good enough, but this is something that you can change later on depending if you feel the included fans are not good enough for your ears. More imporntat, as niel mentioned, that you have a motherboard that can control PWM or 3pin fans, most can do it, but not all, its important to check if the motherboard can control anything you plug in.

Start out by using what you have!

• Is there a problem?
• More exactly what is that problem?
• If too much fan noise, reduce the fan speed and/or adjust the fan curves.
• Do take all fans into consideration. By speeding up a relatively quiet fan you might be able to slow a noisier down while maintaining acceptable temperatures.
• Personally I wouldn't replace any of those fans unless it had some nasty tonality. Better (if needed) to just add more fans and have the lot run slower.