Thanks you Michael and ycarry.
I have tried MiniMagics. Nice viewer, loads the stl file very fast, can import and show many files at once but no way to reposition them with respect one from the another. Worst in my case, the objects cannot be combined at save time.

ycarry, I have tried your suggestion and convert the stl --> obj --> 3dm. The resulting 3dm files contains 129692 Curves :o understandably Moi3d slows down to practically a halt. Thanks you for introducing Wings3D though.

What sotfware would you use if you wanted to make models like the ones shown here? Could this me made in Moi3d?
http://www.vectorart3d.com/store/

Thanks again,
Gaston