I didn't realize the Duo3 has to have an input voltage of 14.5+v to produce full 180watts of power per port. It took a little looking, but I found where the Duo3 had been tested both with PS with > 15v and PS with < 14.5v (RC Groups). Duo3 produced 180watts as advertised with a 14.5+v input source ( 18v was used in the test I found) and it produced 160watts of power when sourced with a 13.8v power supply. Thats a little over an 11% power loss if your supply isn't running at 14.5+v.

The GT350 is a 14v supply and the FeatherMerchant PC server supply is 12.2 or 12.4v (forget which). Neither would give you full power from a Duo3.

I'm using the FeatherMerchant supply, its running my iCharger 3010b and is enough to enable the charger to produce 500watts. That charger requires a 24v supply to produce its full rated 1000watts. Its more expensive that some of the other PC server supplies yopu can find on eBay, but the chaeaper ones seem to have a very loud fan. Mine doesn't, you can barely hear it running.