Here are the settings I use in the IGES options:
IGES solid/surface entities checked, as trimmed surfaces, IGES wireframe (3D curves) un-checked, surface representation as NURBS (standard doesnt work), export 3D curves and sketch entities un-checked (unless you need them), use high trim curve accuracy checked, and for assembly settings, I check save all components of an assembly in one file, but un-check flatten hierarchy. This should get you app your parts grouped into nodes, in the correct world-space, but will also get you copies of the surfaces. Select the nodes and either invert the selection or hide them and pick the free surfaces and delete them. It is sort of annoying, but it sure does work.
Good luck.