Well, I may lose all credibility for stating this but, here goes ...
I picked upo some of the Alan Maher littel boxes as part of a local club "group buy". We got a really inexpensive price on them so I thought it would be worth a shot for experimental purposes. I really had NO expectation that they would work at all. So, after about 3-4 weeks I definitely hear an improvement. Yes, there was some improvement within 24 hours of installing them, but after that things changed (up, down, sideways) sound wise, and no, I can't explain why. But they did stabilize after about 20 days.
Yes, these crystals do have an effect and I don;t have any explaination as to why. I have one box on the incoming bundle to my fuse box, one on the fuse to my audio system, one on the outlet feeding my amp and one on the IEC end of the plug into my preamp.
Now, let the derogatory remarks commence. But at least I know that I tried it and discovered a sonic improvement. (Yes, I have removed them and heard a definite degredation immediately, so they seem to be doing something.)