Folks, these are flea watt "designer" amps from Nelson Pass. Since they won't be powering subwoofers, I don't think performance to 10 Hz really matters. The parts and circuit topology's used are "designed" to give a certain distortion spectra to color the sound. In this case, the ACA's sonic signature is similar to the commercial product Aleph J. Using subjective terms, the amp is warm or "tube like" sounding, with a low damping factor.
Nelson offers amps with lower distortion and a higher damping factor like the F5. So if one is looking for vanishing low distortion figures, the ACA is not the amp for you. But if you like the sound of low watt tube amps, but don't want the hassle of tubes, this may be a fun amp to try.
Look, I am not trying to defend Nelson's designs, but there is a reason for his madness and why most folks like the SQ of these amps. It's all about having fun, right