While the power supply is similar when comparing the XPA -2 to the XPA -5, the ouput stage is where the two differ. The XPA-5 uses 2 toshiba 2sc5200 and 2 toshiba 2sa1943 output devices per channel. The XPA-2 uses 5 toshiba 2sc5200 and 5 toshiba 2sc1946 output devices per channel. Better dampening factor ='s much more definition and control off the bottom end. More power , particularly at high level transient peaks.