I would save those high CFM fans for perhaps implementing them into a 4 rotor power supply helicopter, lol.
The heat in these power supplies is going to be all about those switching MOSFET's. If I could find some really good pictures of thermal imaging for the contact area, you'd see that the highest temps are within fractions of an inch of the transistor die area.
This depiction shows somewhat the story:
Putting a lot of air across the circuit board is going to have little effect for heat dissipation for these FET's. It will be an improvement for the transistors that feed the big FET's and the resistors in that circuit. Also helps to cool other components on the board and will add longevity. The big hurdle is how to get the blowtorch effect of 100W trying to dissipate from that small area and causing the case and components to heat up. Mechanical heat sinking and adding fan air across the heatsink is going to dissipate more heat than blowing air into the case is what I'm theorizing.
If someone had a good computer based heatsink with attached fan, it may be close to the right size to attach to the aluminum plate where the MOSFET's are attached. Direct attachment to this heatsink would be even better. IIRC, the bigger AMD processors were dissipating somewhere in the neighborhood of 50W-60W so a computer heatsink is going to help but will still be less than what's required if a Cheapocharger user is running their unit to the max. I have a couple computer units sitting in a box, somewhere, if there is a someone willing to perform the surgery.
That sound you're hearing is like Ken said, involved with probably inductors or transformers. A transformer will click and buzz quite a bit when powered to the max or not attached securely.
