What size ALPHA ?
If you can use an 80MM fan, the 46.9 CFM Panaflo with 38.2 dB is good, little less volume and slightly quieter is the 39.6 CFM @ 32 dB.
Look to get a 3-pin wire harness for connection direct to motherboard. Smaller fan and wires are available from HeatsinkFactory.
60MM fans move low volumes of air at high RPM not too good.
Consider th YS Tech 80MM manual adjustable range of 800 RPM to 3,700 RPM, 10.2 CFM to 48.7 CFM, & 18dB to 39.5 dB
Any volume over 36 CFM and dB below 40dB should be fine.
Set up fan to extract heat out instead of blowing down into heatsink will eject heat from case quickly, as
rear case fan is usuallu adjacent to CPU heatsink area.