In the 300-watt class, Fortron's FSP300-60GRE (PF) provides a convincing power supply unit that stands out above all because of its maximum power of 367 watts. Another plus is the low operating noise: With 27.0 dB(A) at minimum load and 35.3 dB(A) at maximum load, the device is pleasantly quiet.

Among the 350-watt power supplies, the following candidates won us over: We liked the High Power HPC-360-302 DF from Sirtec because of its 393-watt maximum power and low operating noise of 33.8 dB(A) at minimum and 36.8 dB(A) at full load. The efficiency factor of 72% is among the best in the test panel.

The BQT P4 370W from Be Quiet also earned good grades, with an operating noise level of 25.9 dB(A) at minimum and 33.4 dB(A) at maximum load, it is almost inaudible and earns itself a grade of "very good" with respect to volume. The cable length and connection options also get a ranking of "very good". The efficiency factor of the BQT P4 370W is about 70%. Unfortunately the German manufacturer does not offer the PC power supply unit on the US market.

Aerocool's Aero 420P4 is our favorite for performance and design. With maximum power of 455 watts it offers plenty of reserves even for high-end systems. Modding fans will like the unusual design with the three green acrylic windows that allow a look at the components on the interior of the shiny case. In the dark, the LEDs of the two fans light up the inner workings of the case in green. Honorable mention: In the 400-watt class, the Nexus NX4000 has the highest power with 467 watts. However, this product does not shut off when overloaded. Rather, it delivers a voltage outside the tolerance range via the +5-volt line.

In the high-power class above 450 watts the Antec True Control 550 is the victor. With 495 watts the Antec power supply unit leads the entire test panel in the category of "measured maximum power." In addition to very good cable lengths and two connectors for case fans, it offers the option of optimizing input voltage as an equipment highlight. This is done by means of three potentiometers that are inserted into a 5.25" slot on the front of the PC case. This makes it good particularly for overclockers.