we can talk amps that can deliver gobs of current into low impedance loads (op's query asks for what's best in terms of 'stability into 2 or 4 ohm loads')
but separately we can also talk about amps that sound terrific doing so
b is very much a subset of a, let’s not mistake that
speakers like thiels maggies etc need the power/current but they are also very revealing of the sonic quality of what is being fed to them
solving for a does not necessarily solve for b, for best performance, need both