George:
In my home, the only difference in bass response between the Dag Momentum S250 and the Audio Research amps was the quality of the bass
That will be the output impedance of the ARC being 0.7ohm and the D’Ago being 0.2ohm this is 3 x the damping factor in favor of the D’Ago, the Gryphon is 0.02ohm 10 x better again than the D’Ago, and with even more current available.
The bass of the Alexia which is at it’s worse .9ohm epdr.
That’s why they’re so hard to drive to their best in the bass.
All this is reflected in what the reviewer and tester found with the D’Ago
Overall, the Momentum’s sonic personality, its high-frequency transients somewhat more relaxed, its bass performance ever so slightly less muscular
The output impedance was moderately high for a solid-state design, at 0.21 ohm at 20Hz and 2kHz
And that was on the Wilson Alexandria XLF’s
https://www.stereophile.com/images/113Walexfig1.jpg way easier to drive than the Alexia’s in the bass
https://www.stereophile.com/images/1213Walexfig01.jpgCheers George