Although it would completely ruin the idea, a better solution would be to have each topic a car within a carpark. Then you'd have an excuse for them changing position when you click sort, however, I doubt anyone would play.
How about... each house is dotted around, and when you want to sort by date, it rotates the camera angle all the way around and to a "different angle". Like that you'd miss the way the topics changed position, unless there were only a few, or you were extremely well orientated. But that wouldn't work in 2D very well, and would only work in 3D if you were very good at it.