Just browsing the Esoteric website and cannot seem to find the differences between the S02 and S03 amplifier.
http://www.esoteric.jp/products/cata...02x_s02_en.pdf
http://www.esoteric.jp/products/cata...3xs_s03_en.pdf
Everything seems to be the same, Power Output, Frequency Response, Signal-to-Noise Ratio, Total Harmonic Distortion, Gain, Damping, Inputs, Impedance, Power Consumption and Weight.
Only thing is the dimensions, the S02 is only very slightly larger in Depth.
What justifies the extra $$$$?