Along with the amp I would imagine speaker cable selection would be critical as well?
Yes, that's true, Rja. Speaker cable effects will tend to increase as speaker impedance goes down. Atmasphere among others has made that point in some past threads.
Since it seems that speaker cable effects can't be entirely explained or predicted technically, at least in a manner that stands up when analyzed quantitatively, it's hard to give a complete explanation for that, however.
But among other factors that may be involved, resistance and inductance (or more precisely inductive reactance, the inductive form of impedance) assume greater significance in relation to speaker impedance as speaker impedance becomes lower. Which increases the consequences they may have as a result of the voltage divider effect
Likewise for the rise in resistance that occurs at high frequencies as a result of skin effect, although whether that may be audibly significant under most reasonable circumstances is debatable. Also, although again its audible significance is debatable, lower speaker impedance is likely to worsen the mismatch between speaker impedance and the "characteristic impedance"
of the cable, which will to some small degree affect inductive and capacitive energy storage in the cable, and waveform reflections and RFI pickup that may enter the feedback loop of the amplifier, if it has one.
There are probably other effects that are involved as well, but those are a few possibilities that come to mind.