Kind of driving off-road here, but in a difficult case like this I would make the sphere and the tube in real 3D with Blender, and thereafter would paint over missing details if any.

Xara is powerful, but realistic 3D with reflections is a totally different field.
You'll get much more quick, easy and precise results with a dedicated 3D software, that's for sure.

Keep up posted on this picture, is an interesting challenge.