I am not ddk, but IMO a substantial difference will be seamlessness through crossovers and the apogee seeming more like a single driver. The ribbon midrange. And I have heard the X1 only once, in Italy with an ML 32 pre and the 33 power, and that system was extremely dark. Rolled off, more so than latter day Wilsons including Alexandria, sophia, Sasha, Alexia, etc. Whether it was his speaker or system I do not know.
It's not the Wislons Ked, you're describing the 32 and Levinsons were always dark on top even the 33 to a certain degree and MIT cables I had at the time made everything even darker.
david