First 5 – 7%? I’ll presume this initial area pertains directly to the scenario you presented, otherwise, isn’t the first 10 – 20% of a class AB amp where one finds Class A functionality, and many adore that area of operation.@blindjim Well they do say its all about that 1st watt, but in the case of less efficient speakers it might be about the first 5 watts in the case of some behemoth amps.
(If you've ever heard the maxim that lower powered amps tend to sound better, this is one of the reasons why. IMO, there are some fairly musical low- and mid-powered solid state amps, but there aren't any that are really high powered. As for tube amps, there are very few high powered amps that sound like real music either!)
Class A is helpful for reducing distortion. Most AB solid state amps go from class A to AB within the first watt or so. But even class D amps which operate on a different principle (as well as many push-pull tube amps) have this quality of increased distortion at lower power levels. So even if they were all perfect voltage sources, you would still want to match the efficiency and power handling of the speaker against the low power distortion issues of the amp.
For this reason, I suspect our grandchildren will still be talking about equipment matching- we're not seeming to be solving this issue anytime soon.