I think how bad it is depends on how long you play the ZMA without a load. The longer you do it the worse it gets, but I can’t put any numbers on it. Maybe Steve could. What would solve the problem is swapping in e.g. 8 ohm dummy loads when you swap out the speakers, if you can figure out a way to pull that off.

Apologies for the bit of a delay!

I chose the ZMA somewhat as the Dirty Harry choice, the most powerful amplifier Decware makes!  

But on the serious side, what the ZMA does is gives people freedom to choose whatever speaker they'd like.

Now, yes, with the Forte IV, extremely efficient, the chart shows that people could get by with the SE84UFO series at 2 watts. And many many people made this prudent choice, and are enjoying it with their very efficient speakers. But someday, maybe I'll get a different speaker, and the ZMA will handle it.

Another aspect somewhat overlooked IMHO, but Mr. Deckert prominently mentions, is the massive capacitors for the power supply. Quoting:
"In fact, these capacitors are so large that the amplifier sounds as if it's being run on batteries. It is where the liquidity comes from in the sound.  Clean power is everything with transparent amplification, so when you consider the cost of a power re-generator is more than this amplifier -- the value becomes obvious."

I looked up and AI said that the ZMA and Forte IV were "an absolute dream pairing."