I was thinking of picking up these
Noctua NF-P12 redux-1700
they are 25.1dba, 2.83 mmH₂O for 70.8 CFM
Unless you actually need the industrial ratings on the iPPC variant, this thing is no-frills and nearly half the cost. Seems like a good trade over the stock fans and only losing out on 2CFM
The slight caveat of them only being in 4pin pwm config (in case that matters to people)
I might even split the difference and do the iPPC in the front and redux in the back.