I can answer my own question above as I recently acquired the AA prima. compared to the stock xa777es the prima's soundstage was only slightly smaller with a sound that was slightly less room filling but big enough that it was still very very enjoyable. the xa777es did have better tonal balance (ie more seamless across the frequencies)but I dont know whether that is only because relative to prima the sony was far more dull with less sparkle and excitement and in that, the whole musical presentation "appears" more seamless. the sony is really good and i like what it can do but my personal tastes edged out and preferred the prima. easily. the sony to me seemed more "brainy" while the prima more "heart" without being tubey. The prima seemed closer to being a "musical instrument" and the sony more closer to being a "machine"
the sony was very resolving but it didnt lift the information to the level of emotion and music as could the prima. This is a bigger fault imo than a slightly smaller soundstage and a little less tonal balance. both machines are "great" and i suppose I could live with either but having "tasted" the prima I like what it does and so it will stay in my system and be enjoyed.
