I have not tried this, and would not recommend it unless you have this in a climate controlled room. The PSU puts out a fair bit of heat, and even without the top of the enclosure on, the rear case fans will have a hell of a time cooling both that AND the HDD's themselves. The only way I can see that working, is if you installed very high CFM/RPM fans, and then it would defeat the purpose, as it would still be loud. Installing the 40mm Noctua fan in the PSU really is the best option. It's not that much work, only takes a couple minutes to disassemble the PSU. You just need to splice some cables (with a soldering iron preferably, but you can just use twisted wires and electrical tape instead if you're really lazy).