Interesting hack...going with a bigger fan makes it easier to go quieter since you can run at a lower RPM to move the same amount of air. I just recently replaced a noisy stock 60mm Canon fan with one (NMB ~$ 8) from DigiKey and while not silent, it is much better. Adding rubber mounts/gaskets might help a little with the acoustics. I am trying out a "specialty" replacement for another analog board I am tinkering with that is fairly quiet (slightly lower RPM) but like mentioned earlier, is more expensive.