very interesting topic. I'm not sure if the lack of smooth panning is caused by the speaker. Perhaps one of your components is causing it to not feel as real as it should.
As far as the speakers are concerned. Axiom speakers aren't 'warm' like, say, Paradigm's monitor series. They're very neutral and balanced. The M3's, however, have a slightly recessed midrange, which does sort of make them warm.
I assume you feel your rears are not dispersing sound properly. The soundfield sounds flat, correct? In this case, the QS 8's will definitely help with that. The VP150 will REALLY make dialogue clear.. clear as day. The M50's I hear are excellent, as well, but I have never heard them. Other people will testify that they are great.
Have you also considered changing the placements of your side speakers? I find placing them slightly in the back sounds pretty bad. For music DVD's, they sound good slightly in the front, otherwise it sounds like the band is behind you. For movies, I like it right in the middle.
Keep posting your questions! Lot's of people here will have good advice for you!