On the File Menu is SpaceClaim Options at the bottom. You will see the Graphics performance options. Change the Renering quality from the default of 5 to 9 or 10 and you see a circle rendered with a large number of facets. The numbers 8, 9 and 10 are colored red to warn you that if you have a lot of geometry on the screen, increasing the number of facets to such a large number is going to result in dynamic rotation performance penalty.

You can perfecly align two circles to be concentric without turning up the rendering quality by using the Assemble tools, such as Align on the Assembly tab. You may need to put the geometry into a component to use this, not sure about that.