When it comes to swapping out the fans, be sure that the stock ones use some form of standard connector (2 pin D connector, 3 pin, 4pin). If they are soldered to the PCB, then I do not advise you swap them out. Not that it wouldn't work, as I am sure it would, but it is a lot riskier, and you could potentially blow up the fan controller, like I did.
Just be careful.
I graduated from college in electrical engineering and ive been doing custom car stereo work for almost 20 years, unfortunately not a stranger to a soldering iron and repairing PCB components and whatnot. I do appreciate the heads up, already been doing some research. What was your reason for not using the Noctua 40mm fan? Did your PSU supply 12V or 5V to the fan?
The main reason was the lack of static pressure. Since the stock fan was intended for pulling air all the way though the PSU, high static pressure was necessary. The noctua really didn't cut it (which surprised me, especially knowing the company's reputation).
Also, the fan was 10mm too thin. Now, gap filling would have corrected that issue, but like I said before, there was not enough air pulling through.
The PSU used 12v for the Fan. The specific stock fan was a Yate Loon D40BM-12C.