A larger heatsink with larger fans will always be quieter, in principle. A non-K i7 can probably be cooled adequately by the NH-U9S. You might not even need two fans on the heatsink if you add an intake fan to the rear panel. For the NH-C14S I think you are limited to a fan on the underside of its fins with the window side panel. I'm not certain. Another consideration with a window side panel may be which cooler will look better? The C14S will definitely block more of the view.
Ahh i see, so the audibility for both the U9S & C14S should be similar? I did a bit of searching and heard that the C14S wont fit into the M1 without some tweaking, what are the considerations I need to take into account when installing a C14S IF it is quieter than the U9S?
As for the fan configuration how should I do it so that it would be on the quieter side?
Using the U9S -
Exhaust port - NF A9
U9S - Single NF A9
Accelero III - Remove fans, replace with 2 NF F12
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Using NH C14S
Exhaust port - no fan
C14S - Single NF F12 on the bottom
Accelero III- Remove fans, replace with 2 NF F12