Get the biggest best amps you can.I would agree with this statement. I also have the B&W 805 D3 (previously had D2). I tested two amps side-by-side with these speakers. One set were 250 watt monoblocks and the second set was 500 watt monoblocks. The were the same product line from the same exact manufacturer. The 250 watt amps were nice, but if you listened closely, the smaller 250 watt did not have quite as much authority with bass (not quite as full bass and not quite as much slam). It was almost splitting hairs, but the difference was there. I think a 50-100 watt amp would sound even weaker (but it would still work).
300W RMS, or larger.
You need the headroom, said,many times, when crescendos, drum, or guitar solos, or the song ending slam at the end does happen, you will need the headroom.
You don't buy big amps for the total power. You buy them because they have huge power supply capacitance and transformers. You will get a lot more punch, slam and midrange/midbass body. The smaller amps with smaller transformers and capacitance just will not have the authority, EVEN AT LOWER VOLUMES.
The McIntosh sound is more of a mild and laid back signature. If you say the autoformers create the McIntosh sound, it could be that the autoformers are responsible for the mild/laid-back sound. Just a thought. Not arguing against McIntosh. It's entirely a personal preference.
Just food for thought.