Difference between amps

Everything comes down to the power supply.
You need to scale amps like they are welding machines :-)

A proper amp needs to be able to have about 300-400 watts of supply for every 100 real watts rms class A/B, 600-700 watts of class A of output, all frequencies driven.

So, in a 5 x 100 REAL watts/channel amp, 1500 - 2000 watts of power supply is needed for class A/B and 3000 - 3500 watts of supply is needed for class A. Since that is one HUGE COLLOSAL supply, it is very difficult to have a multichannel amp having the full dynamic range over every channel. Look at the power supplies that come with Pass Labs amplifiers and you will know what I am talking about. And remember that those are only for 2 channels. Imagine what they would be like for 5 or 7 channels.

Otherwise, there are not that many differences between them. Amplifier design is pretty well established & known. The rest is dependent on the quality/longevity of the components used.

@millercarbon
hey dude, my new harbeth 30.2s are under 90 dB sensitivity and easily driven with my pass xa30.8. Sound phenomenal. I’d take a breath before making all these new rules.

@cakyol
interesting points. Perhaps a bit overstated? What kinds of amps and speakers are you talking about?

I'm with cakyol on this one all the way.. I have an older Adcom 7500, it shares a common PS. It works well for what it was intended 20 years ago.. It still works quite well as far as sound and easy to maintain. AB unit doubles watts to 4 ohm. Workhorse.. They used good parts too.

I have a Nord. Class d. It has 3 separate SMPS 1200A700 power supplies, one for each of NC500 amp module. Weird thing, a single 15 amp IEC fused AC plug.  Left me scratching my head. I'll tell you what. It is a sweet 3 channel amp, the BEST I've ever heard That's saying something.. Three separate amp with GREAT class A Sparco pro OA and Sparco regulators.
15 times lower output noise than IC regulators. They have 52dB (about 300X) better rejection of any noise coming into them, and 4X better load regulation than any other 3 terminal IC regulator.

I also have 3 pairs of their NC500 monoblocks.. (surround system). Very sweet when I use it. Pure analog surround, C45 with Class Ds. cool.
No fancy tool there..

Parasound.. I think is one of the best bang for the buck products out there. Hands down..

Mac. I've never owned a multi channel
I've owned Mac 50 years this spring. I love Mac.

Krell, I've owned monoblocks and stereos.  Powerful, and clinical. Paired with good speakers.. NO JUNK.. Good Electra Stats..small planars, Speakers that use Seas drivers.. good components. Krell like that,,

Nad is good. I don't own one. The neighbor does.. Very nice HT both the 2 and 5 channel Nads sound good. He uses a Krell 7.2 surround..That pre though it's older is a Heck of a stereo unit also..

Outlaw, never heard one

Emotiva, has its place.. I don't use them.. Adcom and Rotel are better SQ wise..

You had quite a cross section to choose from, too..

Regards

I enjoy my AHB2.

"...Only one spec matters: speaker sensitivity..."

I know you have posted this over and over but why limit yourself? Sure efficient loudspeakers make it easy to buy amplifiers, but that eliminates a lot of VERY good top end loudspeakers. I'm not willing to do that but I'm willing to buy an arc welder of an amp if I need to. .