Many users wish for a completely silent, passively cooled power supply. But only those devices with lower maximum output can do the job without some active cooling. Problems become manifest when higher outputs are needed for a long time: none of the fanless power supplies could run more than an hour at maximum power ratings of over 300 watts. In that sense, the Antec Phantom 350, the Silverstone SST-ST30NF, and even the Yesico FL-420TX all fail to deliver. But in reckoning the usability of these devices, note further that in more normal modes of operating - such as running typical office applications, or surfing the Web - these units remain stable (and quiet) for days on end. But those users who want to play high-end 3-D games or who encode video data for hours on end will not be happy when their machines shut down after an hour or so of full-tilt use. In those situations, this kind of power supply just won't cut it.

Elan Vital's Greenerger SSM and Epower's Lion 450 hold up even during heavy use. But that's because neither device uses purely passive cooling. At normal half-power operations (250 watts for the Greenerger, and 225 watts for the Lion) neither unit made any noise. Only at high loads do the fans turn on, and they're never loud enough to be objectionable. This lets users count on relatively quiet hardware that keeps running even at heavy loads.

The Lion is attractive because of the many fans it can manage, which permit the computer to keep cool. When loads are low, fans are all quiet, but at high loads all important system components stay cool. The Greenerger SSM is attractive because of its high operating efficiency (at half-power load it leads the pack with a 79% rating). Either unit is a good buy for home theater, media center or other small form factor PCs where silence truly is golden.