Evie, I feel your pain about the wrens. Been there, done that, bought the DVD. I NEVER let them successfully nest here.
If possible, move ALL of the boxes and face them in a different direction for a while. There is no guarantee that a wren won’t find these openings but at least he will have to hunt for them a little. Get them as far away from brush and woodsy areas as you can. You could even temporarily block the holes to further confound him.
The article: http://audubon-omaha.org/bbbox/wren.htm It’s long but worth the time.