If you are building a silent PC or a home theatre PC, you are going to have to go all the way with silent components. This includes the Power Supply.
Unfortunately, most silent power supplies are only silent when they are within a certain temperature range. Once they are above that range, they are anything but silent.
That's why many manufacturers are releasing fanless power supplies! SilverStone is one of them, and their SST-30NF looks to be perfectly designed for silent PC builders looking for the perfect combination of power and silence.