For sale are a pair of Shakti Hallograph soundfield optimizers. These units both diffuse sound waves and resonate across a wide band to create a deeper and more involving soundstage. One of the few acoustical tweaks I've tried which actually have a very discernable and positive effect.
See the following reviews:
Enjoy the Music:
Stereo Times: http://www.stereotimes.com/acc051007.shtml
The condition of the Hallographs are good. No major scratches, just some subtle ones here and there with age.