Well here is my commentary on the Sanus EF-28.
I am using them with the HB's in a room with regular height plush carpeting.
With the HB's on top they are a bit top heavy and wobbly. I would recommend against them if you have large pets or small children that would likely knock into them.
For me they were a relatively cheap option and I went off the recommendation. In the future I would probably spend a little more and get something with a more solid base.
If I can help answer any other questions, or send some pics I'll be more than happy to.