Amp's nominal power rating - any use?

Amps are rated into resistive loads which says next to nothing about how they do into a reactive real world speaker.

I would propose that amps be rated into 8 and 4 ohm resistors....
Than at the same 2 impedances into +-45 degree reactive loads.

The resultant chart would be a very visual indicator of how the amp does into real loads.

That's the way .....at least on paper to see what an amp can be expected to do.

Irv,
I just reread my response and will pretty much stand by it.

Just for an unreal example, a phase angle of 90degrees will result in ZERO power making it to the load. Using the 4foot fluorescent tube next to my workstation as an example, it draws about 1/3 amp. This lamp is consuming about 40va or 32 watts....the power factor is 0.8 and the phase angle is about 37 degrees. The math? PFxVA=Watts.

Tube amps do not like some reactive loads. An 8 watt SET working into a 60degree phase will deliver HALF its rated power to the load. SS is subject to the same limits. But, the amp may not even do that well....half is the upper limit.

I have not seen enough data, but would go out on a limb and say that many amps, even some highly touted ones, won't even do as well as a straight theory calculation (cosine of phase angle x power) says it should.

http://stereophile.com/standloudspeakers/807sonus/index4.html

Stereophile measures of recent version of the SF Guerneri.

Original speaker....from the 90s.

http://stereophile.com/standloudspeakers/487/index5.html

Couple of points....and some agreement.
Yes, phase and impedance ARE frequency dependent.
I think the main take-away would be that a large phase angle coupled with an impedance dip is an amp stresser....(is that a word?)

Also.....and I don't remember which, Tube amps simply do not like a very reactive load. Capacitive? Inductive? don't 'memeber which.
Their is a good reason for this to do with transformers, right?

I don't believe 'next to nothing' is a fair characterization. Given that the PAIRING is a most important aspect to choosing amp/speaker combos, you can't simply ignore phase/impedance characteristics of the load and the amps response TO such loads.

Overcome a 'weird load' with simply more amplifier power? A solution, of sorts. I've heard talk of 'cheap watts' which is one answer. Another approach is the rational design of speakers.... We've all heard of some of the wacky stuff out there which apparently need something from Lincoln or Miller to drive.
I'll leave that decision up to YOU!

Now, about a proposed amp test? I think I'd like to see some data before I simply tossed that out. A resistor may be a nice, standard way to test an amp, but has little or nothing to do with real world conditions. Even my panels have reactive elements, though the impedance curve is pretty flat with only a rise at the crossover frequency. I'd love to see amps tested for power with real world reactive loading. A simulated speaker load could be agreed upon. The worst loading should be below....say 1khz, where most of the amps power goes, anyway, in real music.

And as for the OP's speakers. Fine stuff. Pricey and apparently worth it to some. I can't possibly criticize that choice. But, I would caution the owner to look at the pairing amp carefully. A large phase angle load, regardless of impedance, will still eat into amp power. Large impedance swings also, IMO, kind of defeat the purpose of tube amps. The more recent stereophile test of the similar SF speaker says you may want to use the 4 ohm taps, even though a straight look at the impedance curve may indicate the8 ohm taps.
If I wanted tubes with that speaker, I'd for sure try both.
The OLD test by stereophile did not measure such phase data. The new test indicates moderate phase and impedance curves....probably not a bad load for tube OR SS..