Reminder: how to tell current from an amp's specs?

I can't believe there is even a debate about this. It is well known that driving a speaker that has a variable impedance curve that dips below 4 ohms with an amp that cannot produce the appropriate current at the low impedances will change the frequency response of the speaker. It's a well documented fact. If you can produce evidence to the contrary please do so.

If the amplifier is able to act as a voltage source at less than full power then the contray is certainly possible. For example the Osiris amplifier that @akg_ca mentioned can't double power at full power as load impedance is halved, but at lesser powers it can. In a case like that when the current demand is exceeded, rather than changing the FR the amp will simply clip.

The REGA Osiris integrated amp is one of these exceptions. While it is a beefy hi-current and high WPC amp that doesn’t fully double down, it still has LOTS of current because of its high-end build and design. This is provided by those four Sanken output transistors per channel, that insure that no speaker is too hard to drive.

This statement is incorrect. The extra transistors make sure the output section can support the current without damage but if the power transformer lacks the current capacity it really won't make any difference.

 To me, a big honkin’ transformer (sorry Ralph) and the ability to double down to 4 Ohms and maybe double again down to 2 Ohms is a good indication an amp has the balls to power most speakers

This is generally correct but if the speaker does not have any low impedance dips it could be a waste of money, especially on Maggies which do not have such low impedance dips.

I should point out also that not all speakers that dip to 2 Ohms need a lot of current capacity in the amplifier; Wilsons are a good example. They can easily be driven by tube amplifiers even though the low impedance dip is in the bass. Generally speaking Wilson loudspeakers have traditionally been easy to drive.

If I can point something else out: Just because your amplifier can drive to 2 Ohms and is able to double power as it does so does not mean its sounding its best when doing so. All amplifiers make higher distortion when driving lower impedances! If you think that distortion is inaudible think again- the increased distortion is audible as increased brightness, harshness and a reduction of detail (distortion obscures detail) because most of that added distortion is unmasked higher ordered harmonics.

Let me ask it this way. I've repeatedly read that some speakers, notably Maggies, thrive on high current amps.

@northman 

It really doesn't work that way. What is important is if the amp can drive the load with its rated power. If it can't obviously it will clip prematurely.

The 'current' is surprisingly small. Let's say you have 4 Ohm Maggies and you're driving them with 200 Watts. The Power formula tells you the current:
Power = Current(squared) x Resistance

Power is 200 Watts

Resistance is 4 Ohms.

The current is thus about 7 Amps. Not that much really. So if 400 Watts then 10 Amps; still not that much.

Current cannot exist without Voltage; together they are Watts.

You might want to read this:

Amplifier myths

The 'current' you read about so often with much larger numbers is actually something else! Read the article at the link.