Came across this old thread.
I am now running OHm 100 S3s and 5 S3s with a pair of Bel Canto ref1000 mkii Class D IcePower monoblocks and can offer up some actual observations on this topic now.
CondoCondor nailed it. "grip" is the right term to describe the main difference between the new Class D versus the old Musical Fidelity A3CR, other than the jump to 500 versus 120 watts/channel into 8 OHM, which helps out nicely at louder volumes with the 5s in particular.
The Bels do seem to deliver a vice like grip in controlling the drivers, especially the big 5s, which is just what the doctor ordered. Bass comes across as leaner at first but in fact is delivering the goods in a fast and most rock solid manner, like an MMA fighter in peak condition!
Using the sound from from excellently produced live concerts I have attended recently in smaller venues and some very high end systems I have heard as a reference, this is a big step in that direction. They really do not sound like speakers hardly at all any more at this point.
I have to say that the MF A3CR amp was an incredible piece as well with many similar attributes, but it did not quite have the vice like control of the Walsh drivers that the Class Ds do, but then again the MF amp cost me less than 1/5 what the Ref 1000 mkiis did used.
One thing unique to the ref1000 mkiis which probably contributes to this somewhat is the 100K I believe input impedance for unbalanced input (200K for balanced I believe) which helpss it mate well with a tube pre-amp. That was the thing that helped convince me to go with this particular model. That is a small bump up from the 72K ohm input impedance of the MF A3CR prior, which was also very good compared to most SS amps. The Wyred amps have 62K or so input impedance as well, which is good. Stock Icepower modules have only 10K input impedance I believe, so that is something to consider for those considering using Icepower with tube pre-amps.