Grandtech,
Your comment about the dynamics, looking up the theil model and my own experience with the Atlantics tell me that your surrounds are overmatched by a 12k pair of fronts. My suggestion is to go with a highly dynamic pair of in ceiling. Triad, Revel, B&W come to mind immediately. Your Atlantic tech are also likely only able to go down to 80hz, as most of their stuff crosses over at that point. You may be having some room response issues as a consequence. The only way to know is to do a room response graph for those speakers via the anthem. See where they are getting crossed over. It may be that they are getting crossed over at 120hz or higher and the sub may only be going up to 80. Thus, you might have a frequency gap. But look at the anthem post correction graph to see what's what. In fact, take the next step and post the graph on the AVS forum for the anthem AVM50/D2 forum and see what other opinions you get. While I certainly do think that it is a speaker matching issue, it may also be another issue related to the room. Again, I'm assuming you have property run ARC.