Starting off with Antec's Signature 850w, most people would assume that a power supply with an 80mm fan would be loud. In this case, you'd be wrong. With general usage, including some gaming, the Signature remained quiet throughout. By quiet I mean I couldn't hear it over ambient noise. It was only until our full load test did I hear the little 80mm fan. The fan noise was clearly discernible, but I would assume that if the power supply was installed in a case, you would have difficulty hearing it. In a good way, I was honestly surprised by the Signature and its low noise generation. The Cooler Master UCP 900w was pretty much silent when just playing around on the computer (including some gaming). When subject to our full load test, fan noise ramped up. It was the loudest of the bunch during full load testing, but interestingly, the air exhaust from the power supply was the coolest. It looks like Cooler Master is a bit more aggressive in terms of cooling performance versus noise. Thermaltake's Toughpower Cable Management 1000w was quiet all around. From idle to gaming loads, it was silent. This should be no surprise since it uses a 140mm fan for cooling. During the full load test, fan noise increased, but it was still only a light hum with a whooshing of air. The Toughpower 1000w was the quietest during the full load test. All in all, the three of the power supplies were silent at idle and typical gaming loads. During the full load test, the Thermaltake unit was the quietest, followed by the Antec PSU, with the Cooler Master being the loudest.
In this comparison three high end power supplies were examined. Unlike value oriented product reviews, it was hard to find faults in any of the products. From build quality to operational performance, all of the power supplies killed it... they were all phenomenal. Antec's Signature 850w (SG 850) With the Signature 850w power supply, Antec achieved what they wanted. From an engineering design standpoint, the Signature supplied the cleanest power of the three, which is an amazing feat considering it operated with the highest load percentage of its maximum rated output. It ran surprisingly quiet considering it used an 80mm fan for cooling. The only wish I have for the Signature series from Antec is to release a 1000w version or higher for the high end CrossfireX and SLI users.
Cooler Master's UCP 900w (RS900-AAAAA3-US) Cooler Master did a good job with the UCP 900w power supply. It's targeted to high end users with dual video card rigs, as the 1100w version of the UCP addresses the needs of higher end systems. The real area where this power supply excelled was in efficiency. It used significantly less power than its competitors, which translates to lower power consumption and less heat generation. The only real knocks I have against this power supply is that it's not modular and that it was the noisiest of the bunch in our full load test. Most other current model power supplies in this price range are modular.
Thermaltake's Toughpower Cable Management 1000w (W0132RU) The Toughpower CM 1000w PSU should have no problems with almost anything you throw at it. It performed great while remaining quiet, even with a triple 8800 GTX's in SLI. ALL of it's peripheral connectors are modular, which earns it lots of points. It's a high end power supply that does it's job well. There's nothing really bad to say about it.