I've come to an initial decision on the fans. I spent over $1k on new fans as optional upgrades and replacements for the ones already (and soon to be) shipped out. I bulk purchased new, higer-quality 70x70x20 PWM fans. I'm not saying these are Noctua quality, but I will ensure they are PWM-controlled so at least the noise will be adjustable.
My plan is two-fold for S402 chassis purchased with the original non-PWM 70mm fans:
1. Replacement units - If the original fans from your S402 die within the 30-day warranty period, I will replace them with the newer 70x70x20 units (full set).
2. Coupon code - I will offer a coupon code to be used as a discount on any of the fans available on my site (70x70x15PWM, 70x70x20PWM, 70x70x25PWM, 60x60x15PWM, 60x60x15).
I have to wait until I receive the new fan models before I can offer a coupon code as I want to validate the new fans before I offer them for sale - especially after considering the position I'm in now.