A partial response:
I have not moved up the Omega line. I entered the Omega line with the Super 8 XRS as a second system built around a Leben CS600 amp: tube integrated and single driver simplicity.
I believe that I have the first pair of Super 8 XRS that Louis built - I did not order them, he just built them! I asked for a Mundorf cable panel and internal DNM wiring.
So, I cannot compare them, but I can say that after six months of listening I am very happy with them. This includes the famous Omega build quality.
I had expected to miss some of the treble given a single and large driver. That turned out to not be the case. Instead I miss some of the bass that I have with my other system. That is not a problem as I listen to vocal, acoustic and similar music on the Omegas and opera, orchestra and complex jazz on the primary system.
I think these speakers are great value. Highly recommended.