I think that is a Crassula perforata, it grows upright, it has a firm stem that keeps it upright as it follows the light.
June 2010
May 2012
April 2014
I remember you have sedum burritos, you can put that on the outer edge, if you want the cascading type succulent then your Crassula perforata and the key lime pie succulent in the middle. Or you can put the ice plant all around the sides. However, I find the ice plants very aggressive growers, they can easily over run the others.