The SilverStone SX1000 SFX-L 1 kW PSU Review: Big Power for Small Form Factors Today we are taking a look at the most powerful SFX-L PSU on the planet, the SilverStone SX1000. As its name suggests, the SX1000 can provide up to 1 kW of power, an unprecedented figure for an SFX form factor power supply. But does such a powerful PSU have a place in the market for compact computers?