Whose got best class D at this point?

So Stereomojo picked as its ultimate winner the one Class D amd that TAS said doesn't even deserve a seat at the table. Goes to show...

The feedback we have regarding our amps is that they might not be the best choice for a horn speaker. That may extend to many of the other brands as well, but that is just my "best guess". So, you may want to proceed with caution. The sound of "digital" amps isn't for everyone.

I know this is a real novice question, but what exactly does class D mean, compared to Class A?
What type of amp is a Rotel 200 watt?
Bryston 4B SST?
Mac252 ?

I also here something about certain amps playing to a specific level at Class A, then A/B? What is this? What is A/B?

Thanks.

my nuforce ref 9 SEs are working just fine for me, powerful enough for my speakers, fast, detailed, clear as a bell, and no problems with emf for me, waiting for my nuforce p-9 preamp.

I'd like to comment on class d amps on horns. I'm using a tact Millenium MKIII amp on my Omega DUO's which is highly modded.
The tact is quite different than most other amps mentioned here. It directly convert's pcm tp PWM. It is incredibly quite and even at extreme low volumes doesn't lose resolution which is important when using + 100 db efficient speakers.
Class d amps switching a constant voltage on and off. The tact does the same. it differs because it is adjusting thje volate which is beeing swicthed. Very smart. no volumke control in the signal path?
A friend who has the same modded Millenium compared against the latest Nuforce and said with exception of the bass makes them sound broken in comparison especially in the heights.
Just my 2 cents