... It uses Digital Signal Processing, from what I have learned back in school DSP is essential in mobile communications because it allows to dynamically change parameters of frequency filters. How does it all translate into a good PSU?
In broader terms, DSP just means you're modeling or measuring an analog quantity using digital values, and performing calculations on those values.
A typical switching regulator has an analog feedback loop that compares the output voltage with an internal reference, and varies the width of the output pulses of the switcher to compensate for variations in input voltage or load.
A "digital" switching regulator feeds the output voltage into an analog-to-digital converter and implements the feedback and control loop digitally, using a special-purpose DSP, FPGA, or microprocessor.
Either way, the quality of voltage regulation is only as good as the design of the regulator, the quality of the components used, and the DSP algorithms (for digital). Digital isn't *inherently* better, but it allows additional control and monitoring options to be implemented easily in the DSP code (the "Corsair Link" functionality).
I dunno though...like you said it may be overkill.
For 99.9% of desktop PC users, a 1200 watt, $350 PSU is overkill by definition!