While the divorce options suggested are a solution, they also seem a bit extreme. How about you just paint the grills so that it blends with the wall.

http://axiomaudio.com/paint-speaker-grilles.html

In wall speakers with this done would just about disappear. But, having a condo this might not be the best option. If you get on-wall speakers, with a custom finish that your wife picks out and paint the grills then she may be much more happy.