Hi Rocky,
One thing I have found is that acoustic panels improve imaging in the dimension you lay them out. That is, if you don't find very deep imaging, put more behind the speakers. If you find the image is in a line between your speakers, put more dampening above and below the speakers, that is on the floor and ceiling.
Of course, getting rid of primary reflections is the first thing you do, I just thought this might help.
One thing I have found is that acoustic panels improve imaging in the dimension you lay them out. That is, if you don't find very deep imaging, put more behind the speakers. If you find the image is in a line between your speakers, put more dampening above and below the speakers, that is on the floor and ceiling.
Of course, getting rid of primary reflections is the first thing you do, I just thought this might help.