AnandTech published a review of the Antec Signature 850W power supply.
As stated by Antec we will find voltage regulator modules (VRM) inside this power supply that are DC-to-DC converters. This means we will only get the 12V from the transformer and the lower voltage rails are generated by the VRM. Advantages as stated by Antec are short transient response times within the power supply. Furthermore, Antec includes a PWM controlled fan that has the advantage of being able to run at only 10-15% of its normal rated top speed. We will see later that this results in very low fan speeds and therefore low acoustic noises. According to Antec, all of the capacitors are of Japanese make, which is an indication of high quality and performance. The Antec Signature series received the 80plus Bronze certification which means we can expect very high efficiency from these units.
Check it out over here. At 230VAC the PSU has an efficiency of up to 87% and it seems to be very quiet, only at a power draw of more than 600W the fan starts to ramp up. The build quality of the PSU is very good but the reviewer was a bit disappointed to see voltage drops of up to 5% on the 12V rails under load.