One thing about the 4U Supermicro is that it is easy to change the fan wall to one using 120mm or 140mm fans.
I built the following, and just attached it to the metal with 3M Dual Lock:
I just pulled out the original fan wall and put this in place. It probably wouldn’t be good in a case that moved around a lot, but in one that is fixed in place, it’s fine.
These are 2500rpm fans (Iceberg Thermal IceGALE Xtra 140mm PWM) and have decent static pressure and flow. Unless you are trying to use passive CPU cooling, they are more than enough.