Maybe you're going about it all wrong here. This is what I'd do:

Each day, move your speakers out about 1/2". This is so small of an adjustment, the wife won't really notice for a while. By the time she actually does notice, you may have them out by a foot.

In this situation, my wife would (one day) point at a speaker, while looking at me and say something like, "Oh, and by the way, I know what you're trying to do!"

Then because of the dumb, pitiful look I'd get on my face, and by claiming she's the "Stereo Nazi," she'd eventually lighten up.

I refuse to be held responsible for damages.