How does my MF A308 compare to modern integrated amps in the $3000-$6000 range?

no not if its working properly

op did not disclose, but with his good amp, if he is trying to improve overall sq, he should look at source or speakers (assuming room setup is done properly) for areas of substantial improvement for more $ spent... that is where there will likely be more leverage

reminded of op having atc’s only thing i would add is that mf’s are voiced a touch lively - crisp and clear sonically

atc’s need all the power and control of a strong ss amp for sure, but they are also ruthlessly revealing of what is being fed to them

so unless op likes a somewhat sharp, ’crystal clear’ presentation of the music, a sweet sounding dac may well be a smart upgrade... one that has a more full bodied, organic presentation like an ayre codex, mhdt, audio mirror or neko audio etc etc