See this link for your chair http://sketchup.google.com/3dwarehouse/details?mid=e0f16ba60e1deefe427d16763a0ff49. How it was done:
Saved the Febo chair as an obj file( it has 5825 vertices and 11238 faces);
Imported to Mesh lab( it will import 3ds also) and ran through filters: Merge close vertices ( d= .00010251) with 3 merged; removed duplicate faces with abuot 40 removed;
Saved as dxf file and imported to DoubleCad free. Scaled by 10e6 in DoubleCad;
Imported to SU 7.1 free with the result you see. I have not re-scaled yet.
The reason with the step to Mesh lab is because it has a number of filters for clean up and decimation. I have not tried to reduce model size smaller than above. In addition I think Mesh lab is using a older version of dxf and wanted a later one for import to SU.
Note the small artifacts at left/ right cushion back rest/ seat are in the basics model as well as the small ones on seat front edge. You can try different filters in Mesh lab to reduce model size to what you find acceptable.
Good Luck