For 80/100W, I think you can get away with the stock wiring, but it would be best to upgrade the wiring and use additional relays. See:
http://www.varshney.net/SEC/euro_install/
Courtesy of Anuj Varshney from the mbcoupes.com website.
Also, consider 100W bulbs may burn too hot for use in the plastic fog-light assemblies.
Cheers, Andrew Seidel.