Check out Magnepan. They make a speaker where sound radiates out of both sides. The issue is that depending on the model, they don't deliver the same sort of bass that the Mirage models you have deliver. Some of the higher end speakers do.

They are very hard to drive and are pretty inefficient but so were your Mirage's. They have a pretty good dealer network so you ought to be able to go out and hear them. If there is no dealer in the area, I think they will sell to your direct and either way, I think they provide a 30 day in home demo.

I know there are other like the Bob Carver ALS but those are REALLY expensive. This might be a good place to start.