[ECUPirate]

hehe.. didn't think about radio reception...

the rheo's not that bad.. even a small reduction in voltage can quiet down an 80mm fan. 9v=plenty of air flow, MUCH less noise 7v=enough air, no noise really... but if you can hear your monitor, it may still bother you.
PSU fans serve two functions.. they cool the PSU, and the vent the hot case air away. Normally, you've got the hot case air flowing through the PSU, increasing the airflow needed to keep the PSU from overheating. Since all of your components are WC, the ambients in the case should be close to room temp. Thus, you wouldn't need as much air flow. the Rheo should work fine.
I'd try it.

One note... If you've got a "fan controlling" enermax, your 80mm fan is already running at low speeds. The 92mm fan in the bottom is the culprit, and can be run at 5v with a simple switch. With cool case temps, this is fine.