Wow, then if you can tell the two apart you have the golden ears.
Congrats!!
The MCA amps have THD supposedly well below human perception:
THD at 100 W at 1 kHz . . . . . . . .0.0010% 20 kHz. . . . . . . . . . . . . . 0.015%
and exceptional IMD and noise performance:
IMD at 100 W ITU-R (19 kHz + 20 kHz). . . . . . 0.0005% SMPTE (60 Hz + 7 kHz) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............................................................................0.002% SNR, IEC-A, ref. 225 W. . . . . . . . . . . 120 dB
It is truly amazing that you guys can tell the STR (that costs a lot more money),sounds "much better"..
Maybe you should audition some even more expensive, though still relatively affordable amps from Boulder, Krell, Passlab, Luxman, Moon, Theta, Audio Research etc..