I've just purchased a McIntosh MA252 and matched it with my B&W 683 S2s. I did not compare it to other hybrid integrated amps. As an experiment I've also been trying the MA252 with an older set of Dynaudio Excite X14s bookshelf speakers. All I can say is that the improvement over my prior solid state receiver with both speaker sets is dramatic.
Much will depend on the room, placement, media and input devices, but I really found the largest improvement in vinyl music; cleaner more natural highs, more musical detail and really strong bass. A big improvement in CD and Streaming Media is also there, but not to the same degree as vinyl. My cartridge is an MM Ortofon 2MBlack.
The 683 S2s never sounded better; its like they have new life; the X14s now fill the room with sound. I was skeptical that the McIntosh investment was worth the upgrade differential, but now I have no doubts. Still, I can't help but wonder now much nicer a set of new B&W 800 series would pair with the MA252 and that's how they keep us hooked.