I've got a fanless system, not pretty, but silent, and as they say, silence is golden
I basically screwed a waterblock to the top of the heatsinks in a generic PSU. Yeah, it got hot, really hot, but was stable for a 2 month uptime, then I had to reboot for a driver update.
In the end, I got worried about the heat and installed a 5V papst.... I was ashamed of myself
One thing to remember :
PSU's can run at very high temps, I figure, without measuring, but my mosfets were at at least 70 degrees C. And STILL stable for a LONG time.
However, I had to watercool the RAM on my GFUltra, or I was getting crashes from that, because of the zero airflow, even the little bit from your current PSU fan helps a bit.