I played a little bit with PSU and fans of ICX6610 yesterday, did some interesting findings.
Went to PSU rev A and one fan in intake to PSU rev C exhaust with one fan, then two.
Exhaust PSU seems to be MUCH more silent than intake but will require two back fans modules if you want decent temperature. Those tests are made in my garage in winter, where ambiant temp is about 10C (so pretty low).
(The bump in the graph is moving from PSU intake to PSU exhaust w/ one fan, then it goes back to normal once I add a second fan module).
Single PSU Rev.C in exhaust mode is SO MUCH MORE quiet than single PSU Rev.A intake, you would not believe it. It used to litterally scream (high pitch noise, very loud) to being inaudible over servers and Fortigate around it.
To sum it up:
1. Single PSU Rev.A intake + one fan = ~45C, VERY LOUD
2. Single PSU Rev.C exhaust + one fan = ~71C, quiet
3. Single PSU Rev.C exhaust + two fans = ~46C, quiet
I would have loved to test Rev.A vs Rev.C in same configuration (intake/exhaust) as I heard intake vs exhaust makes a lot of difference in noise levels.