I have Mcintosh XR200 speakers and while I love the speakers, I always felt I would like a more dynamic speaker. I've tried a few brands but none were able to change the fundamental dynamics of the speakers until Krell both XD and non-XD. The Krell amps were already dynamic and I don't hear much difference there between XD and non XD.
The only set-ups that match the Krell XD stuff is bi-amping with a tube amp on the mids and highs and a dynamic solid state amp on the bottom end. The Krell XD stuff can just do it all in one box.