Each power supply was tested on the aforementioned system under the same circumstances to determine how well each held up under use. We measured voltages under Idle and 100% Load conditions of each PSU to measure how stable each was. The measurements were made with Motherboard Monitor 5. Load voltage was taken after half an hour at 100 % capacity.
This is a lot information to take in at once but the overall trend is that the supplies did very well. I had my doubts about how stable they would be as things heated up but the readings prove that the manufacturers took this into account and the PSUs were designed to handle this. There were no power problems and each supply ran through the testing without incident.
If you do a little math you can see the SilverStone delivered the most stable power with the Antec very close behind. Both these two were rock solid performers, and though every PSU tested was well within the limits needed, these two were exceptional. The SilverStone would have been flawless if not for a weak +12V line under load.
As the saying goes, you get what you pay for. The SilverStone and the Antec supplies outperformed the cheaper Coolmax and Thermaltake. The more expensive two were aided by active PFCs and more efficiently designed aluminum exteriors. Among the less expensive two there was not much difference but the Coolmax supply slightly outperformed the Thermaltake.
Another issue with a fanless power supply is going to be the temperature change in your case. With less exhaust airflow and a warmer power supply there is no way the inside of your case is not going to run hotter, but we tested to see which ran the coolest, in the case. We found that under both Idle and Load conditions the same trend emerged, the Antec supply increased the case temperate the least, followed closely by the SilverStone. The Thermaltake was next, and the Coolmax ran the hottest.
If you are planning on running a completely fanless system you should probably go with the Antec or SilverStone. Given the power output difference (100W) the Antec is more efficient at cooling its internals as it can produce 350W whereas the ST30NF was only running at 250W. Of course, if you are running a stripped down computer then 250W could be enough, but you should do the math before you invest all that money.