If the size fits I think they are fine. Keep the back open. I have had both a one unit upright rack and a three unit lower rack for in front of a TV. (Salamander).
I think a nicer rack is Timbernation. This guy is a gem and will build any size and any wood combination. Cost is a bit more but a much more lifetime rack. Take a look at his site and call him and tell him exactly what you want.
http://timbernation.com/Highendaudiorack_PopUp.html