I agree with Metaphysics, I think your over dampened. The spikes to concrete should help this and overall focus. You may end up with too much high frequency energy, but my experience with 805's is with bass problems not treble.
loss of bass after filling stands
Have a pair of B&W matrix 805 and purchased Lovan Ballet stands at the suggestion of a local B&W Dealer. Listened to them for a week without filling them. After filling with sand I sense a loss of some low end. Has anyone experienced this. I also have them on marble tiles as my floor is carpedted(over concrete floor). Any suggestions.