Hey, Jaruzel, nice work, professional finish. Well done. Just one criticism - the screws on the DIN connectors are too long :-D
As to your PSU fan problem, I built my 4000 into an old Dell tower and to make it quiet, I ran three 12 volt fans, but all running from 5 V. They are nice and quiet, and together make enough breeze to keep everything cool. Of course, I used a "normal" 250W ATX PSU. You might be able to use the same idea.
Well done.
tony
