How To Measure "Current" In An Amplifier?

Al,
Thanks,  I suspected that zero or minimal NFB would be the preferred setting. 
Charles, 

@almarg  to your point "None of which means, BTW and IMO, that your amp isn’t a fine match for your speakers :-) "

Absolutely. I’m going further to say I have found a great match.

Stereophile review of the Triton 1 indicates "As tends to be the case with a design using a passive high-pass fi lter with a fairly low corner frequency, the electri-cal phase angle becomes increas-ingly capacitive below that frequency; although the impedance magnitude rapidly increases below 100Hz, miti-gating the effect of that phase angle, there is still a combination of 4.1 ohms and –50° at 100Hz, which will require a good 4 ohm–rated amplifer to drive the speaker to acceptably high levels."

In the meantime, despite the fact that Musical Fidelity does not publish a 4 ohm spec for the M6si, casting doubt as indicated previously in this thread as to its ability to drive a low impedance load by virtue of, presumably, high current, I can tell you that under normal listening I can get the Triton’s singing at the amps 9 o’clock volume control position. Basically producing about 1 watt or 90 db at that point. Cranking to 12 o’clock you wouldn’t be able to have a conversation with a person sitting next to you, much like a night club playing outrageously loud.

So unless Stereophiles meaning of "high levels" corresponds to the Who’s record breaking concert ear piercing decibel threshold, I can vouch that the M6si > Triton 1 "match" is outstanding if we are speaking in terms of (point of this thread) "driving low impedance to high decibel levels".

Hi Gdhal,
Your volume control settings would suggest that you have quite a bit of overall system gain.  By that I mean 90 db SPL at a 9 o'clock V.C.position. 
Charles, 

Sure would be helpful for consumers to be provided with such relevant specs to streamline potential shopping considerations.

@charles1dad 

I appreciate that feedback Charles.

I suppose too much gain could be the case, however, my previous post indicating 1 watt and approx 90 db is more or less by ear only. I haven't used any kind of metering. And while I believe those numbers to a rough approximation, as I consider it further it may be a bit less db like somewhere in the 80s (and therefore less wattage too). But it is loud. Many times I've referred to the decibel scale (average home 50, vacuum 70, chainsaw 110, pain 130) or even different descreptions like this http://www.noisehelp.com/noise-level-chart.html lead me to believe I'm in the ballpark.

And, I would add two things. One, not in all cases does the 9 o'oclock position sound loud. I have ran across some source material where I need to go to 10 or 10:30 just to get what I normally would from 9. Second, the volume control does allow for what I'll loosely categorize as "high precision" around the 9 o'clock range. For instance, if I go from 9 to 9:15 or from 9 to 8:45, the difference is noticeably louder or softer respectively.

So without the intention of hijacking this thread, how would "test" or know if they have to much or too little gain?