4-ohm setting with 8 ohm speakers

I don't know about impedance matching, but if you want a high damping factor the idea is to get speaker / amp impedance pretty much as far apart as possible.

4/8 ohm switch or taps on SS? Maybe to limit power into lower impedance loads to make up for an inadequate PS.

The 'best' load for an amp? Probably a resistor. Than it turns into degrees and how well an amp handles reactive loading.

Check out the link to the 'power cube'...not an amp, but a measuring system.
As always, good specs DO NOT guarantee good sound.

http://www.audiograph.se/Downloads/PowerCube_12p_brochure_complete.pdf

Magfan, looks interesting. Do you know any reviews in which it has been used?

Darn good question....and I have NO answer. You'd think if a manufacturer were proud of a top amp, they take the data and Brag.
Considering the cost of electronic test equipment, this would be a drop in the bucket. Stereophile even skips this test. A plain old resistor is good enough for them!

OTOH, Who the heck knows how to interpret this data except for some fringe tehno-geek types?

Than what would happen of some highly regarded amps crapped out in this test?
When testing a tube amp, should you change taps as you change load impedance?
What about tube amps not being happy with capacitive loads? (I think this is right, and it isn't inductive)

I'm dyslexic and don't read a lot of tests, but the plain ol' resister doesn't sound good.