4-ohm setting with 8 ohm speakers

And yet, nobody has said a single word about reactance. This is implied when taking about impedance. Tube amps do not like capactive loads. period. I hope I got that right.
A 'flat' impedance curve? I've never seen one. If their are any crossover components at all, the speaker should 'swing' from capactive to inductive at some point, shouldn't it?
I think damping may be called on for Plato's above comment about 'looser bass' when using 4 ohm taps. With the whole amp OFF, how much resistance would I measure on 4 ohm or 8 ohm taps?

Other than that? Plato makes sense. Use whichever tap you like. I'd add that if the amp runs too hot while using the 4 ohm taps, I'd reconsider either amp or 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

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)