SU>Max Workflow... (We use it almost exculsively for ArchVis)
Go get Accutrans3D (http://www.micromouse.ca) shareware. Export the model from SU by mat to 3ds. Open the 3ds in AT. Use the merge objects by material under tools. Converts all objects to one by mat. Re-weld verts and save the 3ds again. This will import with instanced/referenced mats into Max.
The only downside is if one of your merges has more than 32,767 verts, the max one objets can have in 3ds, dxf or dwg.
Good luck.