I'd love to do a fan swap, but I'd need to solder new connectors on the fans as they use JST(?) connectors.
Firstly I'd need to find some fans simillar to the current ones (Delta FFB0412SHN).
BTW power consumption on one PSU is 28,4w for the '12 and 43,2w for the '18 measured using a kill-a-watt, both empty fully booted.
I've got various connectors about, and plenty of 3/4pin "headers" that can be soldered up to make adapters. Likely I'll go the route I have before, program a 'duino to control the fans based on some inexpensive temperature probes. The 3.3v nanos can be quite low power and if you run them from a little buck converter and not a linear regulator not much additional heat. Just drive the mosfet(s) well (as in proper driver chips or DIY totem pole driver), add a pullup so that if the PWM signal fails or whatever the fans should fail on.
Given the power difference between the two, I'm highly tempted to go with the 12 port so that I don't feel like I need to get another UPS (or finally get a real rackmount one, as the "rackmount" one I have is barely better than the typical 150ish "tower" style for desktops.
Oooooon the other hand looking up how much it's going to cost to breakout 3-4 of the QSFP ports to optical 10G has me questioning this whole idea :-/ DACs are great for what I've got going in the rack, but it looks like around 60 per breakout (10-15 for the QSFP, ~40-15 for the MPO -> LC) The rest would be the same either way.
On the other-other hand, even if I spend say 300 on breakouts (5 breakouts), even going for a 18 port that puts me around 500 total for 20 10 gig ports outside of the rack, and TBH DACs for QSFP -> SFP+ are not really that bad when you consider they replace 4 SFP+ DACs so personally that's a draw price wise. So I think I've talked myself back into it lol.