Reducing CPU clock frequency allows for lower VIDs (i.e. lower core voltages) which means much lower currents. Intel's specification for the E7200 processor is shown.
High power consumption cannot be resolved by simply providing a better PS (Power Supply) as this does nothing to reduce EMI. Currents of up to several amperes is at work. Hence reducing power consumption is essential. Whilst a good PS is vital, how it is used is critical.
A fully specified cMP² consumes less than 20 watts power at maximum load (i.e. upsampling 44.1k to 192k using the most intensive upsampler, SRC @ 145db SNR).