So there is no one measurement available to indicate the “current” capability? I don’t have electrical technical back, and I feel this concept is being mystified…
The problem you’re up against is marketing. Often solid state amps are advertised as having a certain amount of ’current’. That can be quite different from the current required to drive the speaker load properly when the amp is at full power. You might want to read the article at this link:
http://www.atma-sphere.com/en/resources-common-power-amplifier-myths.html
As an additional hint for good sound: avoid loudspeakers that are excessively low impedance (less than 4 Ohms) or low efficiency. The reason is that all amplifiers made more distortion driving lower impedances, and low efficiency loudspeakers (less than 87dB) tend to suffer thermal compression caused by heating in the voice coil. You might think that additional distortion is inaudible (that its 'negligible') but that isn’t the case. The ear interprets all forms of distortion as a tonality and it is keenly sensitive to the higher ordered harmonics since it uses them to sense how loud a sound is (and the ear has over 120dB range)- so more sensitive to those harmonics than anything else! So when your amp has to work hard for a living, the additional distortion it makes will be mostly the higher orders. This contributes to harshness and brightness (the tonality assigned by the ear) as well as a loss of detail, which affects things like sound stage depth and width, as well as nuances.
So the difference in distortion is not only audible its also measurable.